perf tsc: Calculate timestamp with cap_user_time_short

The perf mmap'ed buffer contains the flag 'cap_user_time_short' and two
extra fields 'time_cycles' and 'time_mask', perf tool needs to know them
for handling the counter wrapping case.

This patch is to reads out the relevant parameters from the head of the
first mmap'ed page and stores into the structure 'perf_tsc_conversion',
if the flag 'cap_user_time_short' has been set, it will firstly
calibrate cycle value for timestamp calculation.

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 11059
  mmap size 528384B
  1st event perf time 996384576521 tsc 3850532906613
  rdtsc          time 996384578455 tsc 3850532913950
  2nd event perf time 996384578845 tsc 3850532915428
  test child finished with 0
  ---- end ----
  Convert perf time to TSC: Ok
  #

Signed-off-by: Leo Yan <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Kemeng Shi <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Poirier <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Nick Gasson <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Remi Bernon <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Steve Maclean <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Zou Wei <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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