IB/mlx5: When in switchdev mode, expose only raw packet capabilities

Currently in switchdev mode we allow only for raw packet QPs.
Expose the right capabilities and set the gid table length to 0, also
make sure we don't try to enable RoCE, so split the function
to enable RoCE so representors can enable only the notifier needed for
net device events.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>