RDMA/qedr: Fix rc initialization on CNQ allocation failure

Return code wasn't set properly when CNQ allocation failed.
This only affect error message logging, currently user will
receive an error message that says the qedr driver load failed
with rc '0', instead of ENOMEM

Fixes: ec72fce4 ("qedr: Add support for RoCE HW init")
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: Ariel Elior <Ariel.Elior@cavium.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>