MAINTAINERS: fix REMOTEPROC F: typo

remoteproc.txt should have been .h

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>