If MAINTAINERS section entries are misformatted, it was possible to have
an infinite loop.

Correct the defect by always moving the index to the end of section + 1

Also, exit check for exclude as soon as possible.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>