perf tools: Add aarch64 registers to --user-regs

perf tools: Add aarch64 registers to --user-regs

Previously, this command returns no help message on aarch64:

  -> ./perf record --user-regs=?

  available registers:
  Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

With this change, the registers are listed.

  -> ./perf record --user-regs=?

  available registers: x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 x12 x13 x14 x15 x16 x17 x18 x19 x20 x21 x22 x23 x24 x25 x26 x27 x28 x29 lr sp pc

It's also now possible to record subsets of registers on aarch64:

  -> ./perf record --user-regs=x4,x5 ls
  -> ./perf report --dump-raw-trace

  12801163749305260 0xc70 [0x40]: PERF_RECORD_SAMPLE(IP, 0x2): 51956/51956: 0xffffaa6571f0 period: 145785 addr: 0
  ... user regs: mask 0x30 ABI 64-bit
  .... x4    0x000000000000006c
  .... x5    0x0000001001000001
   ... thread: ls:51956
    ...... dso: /usr/lib64/ld-2.17.so

Signed-off-by: Alexandre Truong <alexandre.truong@arm.com>
Tested-by: James Clark <james.clark@arm.com>
Acked-by: John Garry <john.garry@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20201127153923.26717-1-alexandre.truong@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>