smbfs: fix debug builds

Fix some warnings with SMBFS_DEBUG_* builds.  This patch makes it so that
builds with -Werror don't fail.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>