RDMA/uverbs: remove redundant assignment to variable ret

The variable ret is being initialized with a value that is never read and
it is being updated later with a new value. The initialization is
redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -2548,7 +2548,7 @@ static int ib_uverbs_detach_mcast(struct uverbs_attr_bundle *attrs)
 	struct ib_uqp_object         *obj;
 	struct ib_qp                 *qp;
 	struct ib_uverbs_mcast_entry *mcast;
-	int                           ret = -EINVAL;
+	int                           ret;
 	bool                          found = false;
 
 	ret = uverbs_request(attrs, &cmd, sizeof(cmd));