checkpatch: add tests for function pointer style misuses

Kernel style uses function pointers in this form:
	"type (*funcptr)(args...)"

Emit warnings when this function pointer form isn't used.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Derek Perrin <d.roc16@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>