PNP: skip dev->protocol NULL checks

Every PNP device should have a valid protocol pointer.  If it doesn't,
something's wrong and we should oops so we can find and fix the problem.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Adam Belay <ambx1@neo.rr.com>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Rene Herman <rene.herman@keyaccess.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>