SUNRPC refactor rpcauth_checkverf error returns

Most of the time an error from the credops crvalidate function means the
server has sent us a garbage verifier. The gss_validate function is the
exception where there is an -EACCES case if the user GSS_context on the client
has expired.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index e52d832f..d5d6923 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -192,13 +192,13 @@
 	    flavor != RPC_AUTH_UNIX &&
 	    flavor != RPC_AUTH_SHORT) {
 		printk("RPC: bad verf flavor: %u\n", flavor);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 
 	size = ntohl(*p++);
 	if (size > RPC_MAX_AUTH_SIZE) {
 		printk("RPC: giant verf size: %u\n", size);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 	task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
 	p += (size >> 2);