perf tools: Add Adrian Hunter to MAINTAINERS as a reviewer

Adrian is the main author of the Intel PT codebase and has been
reviewing perf tooling patches consistently for a long time, so lets
reflect that in the MAINTAINERS file so that contributors add him to the
CC list in patch submissions.

Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/ZAYosCjlzO9plAYO@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>