IB/mlx4: Support RAW Ethernet when RoCE is disabled

On some environments, such as certain SR-IOV VF configurations, RoCE
isn't supported for mlx4 Ethernet ports. Currently the driver will
not open IB device on that port.

This is problematic since we do want user-space RAW Ethernet QPs functionality
to remain in place. For that end, enhance the relevant driver flows such that we
do create a device instance in that case.

Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>