MAINTAINERS: TRACING: Add Mathieu Desnoyers as Reviewer

In order to make sure I get CC'd on tracing changes for which my input
would be relevant, add my name as reviewer of the TRACING subsystem.

Link: https://lore.kernel.org/linux-trace-kernel/[e-mail]

Acked-by: Masami Hiramatsu (Google) <[e-mail]>
Signed-off-by: Mathieu Desnoyers <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

MAINTAINERS

···
 TRACING
 M:	Steven Rostedt <[e-mail]>
 M:	Masami Hiramatsu <[e-mail]>
+R:	Mathieu Desnoyers <[e-mail]>
 L:	[e-mail]
 L:	[e-mail]
 S:	Maintained