authgss build fix

Recent breakage..

net/sunrpc/auth_gss/auth_gss.c:1002: warning: implicit declaration of function 'lock_kernel'
net/sunrpc/auth_gss/auth_gss.c:1004: warning: implicit declaration of function 'unlock_kernel'

Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/sunrpc/auth_gss/auth_gss.c

@@ -43,6 +43,7 @@
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/smp_lock.h>
 #include <linux/pagemap.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/auth.h>