net/mlx4: Handle return codes in mlx4_qp_attach_common

net/mlx4: Handle return codes in mlx4_qp_attach_common

Both new_steering_entry() and existing_steering_entry() return values
based on their success or failure, but currently they fall through
silently.  This can make troubleshooting difficult, as we were unable
to tell which one of these two functions returned errors or
specifically what code was returned.  This patch remedies that
situation by passing the return codes to err, which is returned by
mlx4_qp_attach_common() itself.

This also addresses a leak in the call to mlx4_bitmap_free() as well.

Signed-off-by: Robb Manes <rmanes@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>