net/mlx5: E-switch, Fix error handling for enabling roce

The cited commit assumes enabling roce always succeeds. But it is
not true. Add error handling for it.

Fixes: 80f09dfc ("net/mlx5: Eswitch, enable RoCE loopback traffic")
Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/20250423083611.324567-6-mbloch@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>