MAINTAINERS: use tab not spaces for delimiter

Keeps MAINTAINERS a bit more consistent.
done via sed -r -i -e 's/^([A-Z]):[ \t]+/\1:\t/g' MAINTAINERS

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>