userns: Store uid and gid values in struct cred with kuid_t and kgid_t types

cred.h and a few trivial users of struct cred are changed.  The rest of the users
of struct cred are left for other patches as there are too many changes to make
in one go and leave the change reviewable.  If the user namespace is disabled and
CONFIG_UIDGID_STRICT_TYPE_CHECKS are disabled the code will contiue to compile
and behave correctly.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 7eff867..8660231 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -36,8 +36,8 @@
 int create_user_ns(struct cred *new)
 {
 	struct user_namespace *ns, *parent_ns = new->user_ns;
-	kuid_t owner = make_kuid(new->user_ns, new->euid);
-	kgid_t group = make_kgid(new->user_ns, new->egid);
+	kuid_t owner = new->euid;
+	kgid_t group = new->egid;
 
 	/* The creator needs a mapping in the parent user namespace
 	 * or else we won't be able to reasonably tell userspace who