MAINTAINERS: add Masami as a reviewer of hung task detector

Since I'm actively working on hung task blocker detector, add myself to a
reviewer of the HUNG TASK DETECTOR feature.

Link: https://lkml.kernel.org/r/175388550841.627474.3260499035226455392.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: mhiramat

MAINTAINERS

@@ -11438,6 +11438,7 @@ F:	drivers/tty/hvc/
 HUNG TASK DETECTOR
 M:	Andrew Morton <akpm@linux-foundation.org>
 R:	Lance Yang <lance.yang@linux.dev>
+R:	Masami Hiramatsu <mhiramat@kernel.org>
 L:	linux-kernel@vger.kernel.org
 S:	Maintained
 F:	include/linux/hung_task.h