Implements softirq trace bpf function.

Test cases:
Trace softirq latency without filter:

  # perf kwork -k softirq lat -b
  Starting trace, Hit <Ctrl+C> to stop and report
  ^C
    Kwork Name                     | Cpu  | Avg delay     | Count     | Max delay     | Max delay start     | Max delay end       |
   --------------------------------------------------------------------------------------------------------------------------------
    (s)RCU:9                       | 0005 |      0.281 ms |         3 |      0.338 ms |     111295.752222 s |     111295.752560 s |
    (s)RCU:9                       | 0002 |      0.262 ms |        24 |      1.400 ms |     111301.335986 s |     111301.337386 s |
    (s)SCHED:7                     | 0005 |      0.177 ms |        14 |      0.212 ms |     111295.752270 s |     111295.752481 s |
    (s)RCU:9                       | 0007 |      0.161 ms |        47 |      2.022 ms |     111295.402159 s |     111295.404181 s |
    (s)NET_RX:3                    | 0003 |      0.149 ms |        12 |      1.261 ms |     111301.192964 s |     111301.194225 s |
    (s)TIMER:1                     | 0001 |      0.105 ms |         9 |      0.198 ms |     111301.180191 s |     111301.180389 s |
    ... <SNIP> ...
    (s)NET_RX:3                    | 0002 |      0.098 ms |         6 |      0.124 ms |     111295.403760 s |     111295.403884 s |
    (s)SCHED:7                     | 0001 |      0.093 ms |        19 |      0.242 ms |     111301.180256 s |     111301.180498 s |
    (s)SCHED:7                     | 0007 |      0.078 ms |        15 |      0.188 ms |     111300.064226 s |     111300.064415 s |
    (s)SCHED:7                     | 0004 |      0.077 ms |        11 |      0.213 ms |     111301.361759 s |     111301.361973 s |
    (s)SCHED:7                     | 0000 |      0.063 ms |        33 |      0.805 ms |     111295.401811 s |     111295.402616 s |
    (s)SCHED:7                     | 0003 |      0.063 ms |        14 |      0.085 ms |     111301.192255 s |     111301.192340 s |
   --------------------------------------------------------------------------------------------------------------------------------

Trace softirq latency with cpu filter:

  # perf kwork -k softirq lat -b -C 1
  Starting trace, Hit <Ctrl+C> to stop and report
  ^C
    Kwork Name                     | Cpu  | Avg delay     | Count     | Max delay     | Max delay start     | Max delay end       |
   --------------------------------------------------------------------------------------------------------------------------------
    (s)RCU:9                       | 0001 |      0.178 ms |         5 |      0.572 ms |     111435.534135 s |     111435.534707 s |
   --------------------------------------------------------------------------------------------------------------------------------

Trace softirq latency with name filter:

  # perf kwork -k softirq lat -b -n SCHED
  Starting trace, Hit <Ctrl+C> to stop and report
  ^C
    Kwork Name                     | Cpu  | Avg delay     | Count     | Max delay     | Max delay start     | Max delay end       |
   --------------------------------------------------------------------------------------------------------------------------------
    (s)SCHED:7                     | 0001 |      0.295 ms |        15 |      2.183 ms |     111452.534950 s |     111452.537133 s |
    (s)SCHED:7                     | 0002 |      0.215 ms |        10 |      0.315 ms |     111460.000238 s |     111460.000553 s |
    (s)SCHED:7                     | 0005 |      0.190 ms |        29 |      0.338 ms |     111457.032538 s |     111457.032876 s |
    (s)SCHED:7                     | 0003 |      0.097 ms |        10 |      0.319 ms |     111452.434351 s |     111452.434670 s |
    (s)SCHED:7                     | 0006 |      0.089 ms |         1 |      0.089 ms |     111450.737450 s |     111450.737539 s |
    (s)SCHED:7                     | 0007 |      0.085 ms |        17 |      0.169 ms |     111452.471333 s |     111452.471502 s |
    (s)SCHED:7                     | 0004 |      0.071 ms |        15 |      0.221 ms |     111452.535252 s |     111452.535473 s |
    (s)SCHED:7                     | 0000 |      0.044 ms |        32 |      0.130 ms |     111460.001982 s |     111460.002112 s |
   --------------------------------------------------------------------------------------------------------------------------------
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220709015033.38326-17-yangjihong1@huawei.com
[ Add {} for multiline if blocks ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>