checkpatch: add short int to c variable types

short int is one of the 6.7.2 c90 types.
Find it appropriately.

This fixes a defect in checkpatch where it suggests that a line break
after declaration is required using an input like:

	int foo;
	short int bar;

Without this change, it warns on the short int line.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Hartley Sweeten <HartleyS@visionengravers.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>