perf tools: Add long time reviewers to MAINTAINERS

Jiri and Namhyung have long contributed a lot of code and time reviewing
patches to tools/, so lets make that reflected in the MAINTAINERS file
to encourage patch submitters to add them to the CC list, speeding up
the process of tools/perf/ patch processing.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-onicopw68bg6kn56lnybfpns@git.kernel.org


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