checkpatch: notice unbalanced else braces in a patch

Patches that add or modify code like

	} else
		<foo>
or
	else {
		<bar>

where one branch appears to have a brace and the other branch does not
have a brace should emit a --strict style message.

Link: http://lkml.kernel.org/r/c6be32747fc725cbc235802991746700a0f54fdc.1486754390.git.joe@perches.com


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>