failcmd: add script file in MAINTAINERS

failcmd is one of the main interfaces to fault injection framework, but,
it is not listed under FAULT INJECTION SUPPORT entry in MAINTAINERS. This
is unfortunate, since git-send-email doesn't find emails to send the
patches to, forcing the user to try to guess who maintains it.

Akinobu Mita seems to be actively maintaining it, so, let's add the file
under FAULT INJECTION SUPPORT section.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Breno Leitao <[e-mail]>
Reviewed-by: Akinobu Mita <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

MAINTAINERS

···
 S:	Supported
 F:	Documentation/fault-injection/
 F:	lib/fault-inject.c
+F:	tools/testing/fault-injection/
 
 FBTFT Framebuffer drivers
 L:	[e-mail]