genetlink: Make family a signed integer.

The idr_alloc(), idr_remove(), et al. routines all expect IDs to be
signed integers.  Therefore make the genl_family member 'id' signed
too.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/genetlink.h

@@ -48,7 +48,7 @@ struct genl_info;
  * @n_ops: number of operations supported by this family
  */
 struct genl_family {
-	unsigned int		id;		/* private */
+	int			id;		/* private */
 	unsigned int		hdrsize;
 	char			name[GENL_NAMSIZ];
 	unsigned int		version;