checkpatch: improve the STORAGE_CLASS test

Make sure static, extern, and asmlinkage appear before a specific type.

e.g.:
	int asmlinkage foo(void)
is better written
       asmlinkage int foo(void)

Link: http://lkml.kernel.org/r/31704c96df2d5fd9df0b41165940a7a4feb16a63.1499284835.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>