checkpatch: pull out known acceptable typedefs

Within the type checker we have a number of common kernel types which must
be implemented as typedefs.  Pull those out so that we can use the same
expressions to trigger exclusions.

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>