RDMA/ocrdma: Fix load time panic during GID table init

We should use rdma_vlan_dev_real_dev() instead of using vlan_dev_real_dev()
when building the GID table for a vlan interface.

Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>