pnp: fix kernel-doc warnings

Fix PNP docbook warnings:

Warning(linux-2623-rc1g4//drivers/pnp/core.c): no structured comments found
Warning(linux-2623-rc1g4//drivers/pnp/driver.c): no structured comments found

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>