MAINTAINERS: befs: add new maintainers

Salah Triki and Luis de Bethencourt are taking over maintainership of
befs.

Link: http://lkml.kernel.org/r/1469651079-32455-1-git-send-email-luisbg@osg.samsung.com
Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>