MAINTAINERS: assign ./fs/tracefs to TRACING

A check with ./scripts/get_maintainer.pl --letters -f fs/tracefs/ shows
that the tracefs is not assigned to the TRACING section in MAINTAINERS.

Add the file pattern for the TRACING section to rectify that.

Link: https://lkml.kernel.org/r/20201109122250.31915-1-lukas.bulwahn@gmail.comSigned-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

MAINTAINERS

@@ -17751,6 +17751,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core
 F:	Documentation/trace/ftrace.rst
 F:	arch/*/*/*/ftrace.h
 F:	arch/*/kernel/ftrace.c
+F:	fs/tracefs/
 F:	include/*/ftrace.h
 F:	include/linux/trace*.h
 F:	include/trace/