perf annotate: Use architecture-agnostic register limit

Remove the arch-specific guard around TYPE_STATE_MAX_REGS and define it
as 32 for all architectures.

The architecture that perf is built on may not match the architecture
that produced the perf.data file, so relying on __powerpc__ or similar
is fragile.

Using 32 as a fixed upper bound is safe since it is greater than the
previous maximum of 16.

Add a comment to clarify that TYPE_STATE_MAX_REGS is an arch-independent
maximum rather than a build-time choice.

Suggested-by: Ian Rogers <irogers@google.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.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: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>