lib/digsig.c: use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...))

Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/digsig.c

@@ -209,7 +209,7 @@ int digsig_verify(struct key *keyring, const char *sig, int siglen,
 		kref = keyring_search(make_key_ref(keyring, 1UL),
 						&key_type_user, name);
 		if (IS_ERR(kref))
-			key = ERR_PTR(PTR_ERR(kref));
+			key = ERR_CAST(kref);
 		else
 			key = key_ref_to_ptr(kref);
 	} else {