Functions perf_read_tsc_conversion() and perf_event__synth_time_conv()
should work as common functions rather than x86 specific, so move these
two functions out from arch/x86 folder and place them into util/tsc.c.

Since the function perf_event__synth_time_conv() will be linked in
util/tsc.c, remove its weak version.

Committer testing:

Before/after:

  # perf test tsc
  70: Convert perf time to TSC                                        : Ok
  #
  # perf test -v tsc
  70: Convert perf time to TSC                                        :
  --- start ---
  test child forked, pid 8520
  mmap size 528384B
  1st event perf time 592110439891 tsc 2317172044331
  rdtsc          time 592110441915 tsc 2317172052010
  2nd event perf time 592110442336 tsc 2317172053605
  test child finished with 0
  ---- end ----
  Convert perf time to TSC: Ok
  #
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kemeng Shi <shikemeng@huawei.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Gasson <nick.gasson@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Remi Bernon <rbernon@codeweavers.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Steve Maclean <steve.maclean@microsoft.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zou Wei <zou_wei@huawei.com>
Link: http://lore.kernel.org/lkml/20200914115311.2201-2-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>