net/mlx5e: TC, fix decap fallback to uplink when int port not supported

When resolving the decap route device for a tunnel decap rule,
the result may be an OVS internal port device.

Prior to adding the support for internal port offload, such case
would result in using the uplink as the default decap route device
which allowed devices that can't support internal port offload
to offload this decap rule.

This behavior got broken by adding the internal port offload which
will fail in case the device can't support internal port offload.

To restore the old behavior, use the uplink device as the decap
route as before when internal port offload is not supported.

Fixes: b16eb3c8 ("net/mlx5: Support internal port as decap route device")
Signed-off-by: Ariel Levkovich <lariel@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>