ftrace: Maintain samples/ftrace

There's no entry in MAINTAINERS for samples/ftrace. Add one so that the
FTRACE maintainers are kept in the loop.

Link: https://lkml.kernel.org/r/[email protected]

Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: mrutland-arm

MAINTAINERS

@@ -8570,6 +8570,7 @@ F:	kernel/trace/fgraph.c
 F:	arch/*/*/*/*ftrace*
 F:	arch/*/*/*ftrace*
 F:	include/*/ftrace.h
+F:	samples/ftrace
 
 FUNGIBLE ETHERNET DRIVERS
 M:	Dimitris Michailidis <[email protected]>