checkpatch: detect multiple bitfield declarations

Detect the colons (:) which make up secondary bitfield declarations and
apply binary colon checks.  For example the following is common idiom:

	int foo:1,
	    bar:1;

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>