Sort PMUs by name. If two PMUs have the same name but differ by
suffix, sort the suffixes numerically.

For example, "breakpoint" comes before "cpu",
"uncore_imc_free_running_0" comes before "uncore_imc_free_running_1".

Suffixes need to be treated specially as otherwise they will be ordered
like 0, 1, 10, 11, .., 2, 20, 21, .., etc. Only PMUs starting 'uncore_'
are considered to have a potential suffix.

Sorting of PMUs is done so that later patches can skip duplicate uncore
PMUs that differ only by there suffix.

Committer notes:

Used the more compact, intention revealing strstarts() function we got
from the kernel sources:

-       if (strncmp(str, "uncore_", 7))
+       if (!strstarts(str, "uncore_"))

Also in pmus_cmp() the lhs_num and rhs_num variables may end up not
being set for non "uncore_" prefixed PMUs in pmu_name_len_no_suffix(),
or at least gcc 7.5 in some distros (opensuse 15.5, to be EOLed in
Dec/2024) thins so, so initialize both to zero.
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20230825135237.921058-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>