rxrpc: fix uninitialized variable use

Hashing the peer key was introduced for AF_INET, but gcc
warns about the rxrpc_peer_hash_key function returning uninitialized
data for any other value of srx->transport.family:

net/rxrpc/peer_object.c: In function 'rxrpc_peer_hash_key':
net/rxrpc/peer_object.c:57:15: error: 'p' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Assuming that nothing else can be set here, this changes the
function to just return zero in case of an unknown address
family.

Fixes: be6e6707f6ee ("rxrpc: Rework peer object handling to use hash table and RCU")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/peer_object.c

@@ -50,6 +50,9 @@ static unsigned long rxrpc_peer_hash_key(struct rxrpc_local *local,
 		size = sizeof(srx->transport.sin.sin_addr);
 		p = (u16 *)&srx->transport.sin.sin_addr;
 		break;
+	default:
+		WARN(1, "AF_RXRPC: Unsupported transport address family\n");
+		return 0;
 	}
 
 	/* Step through the peer address in 16-bit portions for speed */