And also for 'struct strarray', since its needed to implement
strarrays__strtoul(). This just traverses the entries and when finding a
match, returns (offset + index), i.e. the value associated with the
searched string.

E.g. "EFER" (MSR_EFER) returns:

  # grep -w EFER -B2 /tmp/build/perf/trace/beauty/generated/x86_arch_MSRs_array.c
  #define x86_64_specific_MSRs_offset 0xc0000080
  static const char *x86_64_specific_MSRs[] = {
	[0xc0000080 - x86_64_specific_MSRs_offset] = "EFER",
  #

  0xc0000080

This will be auto-attached to 'struct syscall_arg_fmt' entries
associated with strarrays as soon as we add a ->strarray and ->strarrays
to 'struct syscall_arg_fmt'.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-r2hpaahf8lishyb1owko9vs1@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>