rds: send: Fix dead code in rds_sendmsg

Currently, code at label *out* is unreachable. Fix this by updating
variable *ret* with -EINVAL, so the jump to *out* can be properly
executed instead of directly returning from function.

Addresses-Coverity-ID: 1472059 ("Structurally dead code")
Fixes: 1e2b44e7

 ("rds: Enable RDS IPv6 support")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>