qlge: pull NULL check ahead of dereference

There was a dereference before NULL check issue introduced in 1e213303d
"qlge: Add tx multiqueue support."  I've pulled the NULL check of
"net_rsp" forward a couple lines to avoid that.

Also Ron Mercer says that the early exit should be above the index
write.  ql_write_cq_idx(rx_ring);

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>