keys: fix trusted/encrypted keys sparse rcu_assign_pointer messages

Define rcu_assign_keypointer(), which uses the key payload.rcudata instead
of payload.data, to resolve the CONFIG_SPARSE_RCU_POINTER message:
"incompatible types in comparison expression (different address spaces)"

Replace the rcu_assign_pointer() calls in encrypted/trusted keys with
rcu_assign_keypointer().

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 0ed5fdf..2d5d041 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -993,7 +993,7 @@
 	kfree(datablob);
 	kfree(options);
 	if (!ret)
-		rcu_assign_pointer(key->payload.data, payload);
+		rcu_assign_keypointer(key, payload);
 	else
 		kfree(payload);
 	return ret;
@@ -1067,7 +1067,7 @@
 			goto out;
 		}
 	}
-	rcu_assign_pointer(key->payload.data, new_p);
+	rcu_assign_keypointer(key, new_p);
 	call_rcu(&p->rcu, trusted_rcu_free);
 out:
 	kfree(datablob);