perf tools: Bump default sample freq to 4 kHz

Quoting Ingo:

"While at it I'd also suggest increasing the default sampling frequency,
from 1000 Hz per CPU to at least 4Khz auto-freq or so - this should work
well all across the board I think. CPUs are getting faster and command/app
run times are getting shorter, 1Khz is a bit low IMO."
Requested-by: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2jafa6mkrufyekny9ei59lpu@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -753,7 +753,7 @@ static struct perf_record record = {
 		.mmap_pages	     = UINT_MAX,
 		.user_freq	     = UINT_MAX,
 		.user_interval	     = ULLONG_MAX,
-		.freq		     = 1000,
+		.freq		     = 4000,
 		.target		     = {
 			.uses_mmap   = true,
 		},

tools/perf/builtin-top.c

@@ -1162,7 +1162,7 @@ int cmd_top(int argc, const char **argv, const char *prefix __used)
 	struct perf_top top = {
 		.count_filter	     = 5,
 		.delay_secs	     = 2,
-		.freq		     = 1000, /* 1 KHz */
+		.freq		     = 4000, /* 4 KHz */
 		.mmap_pages	     = 128,
 		.sym_pcnt_filter     = 5,
 		.target		     = {