ofed: fix roce gid insertion for vlan interfaces

When attempting to use vlan interface the correct GID
wasn't created due to incorrect ifp validation.

The problem was introduced in
3e142e07675b ('ofed: Mechanically convert to IfAPI)

Signed-off-by: Bartosz Sobczak bartosz.sobczak@intel.com
Signed-off-by: Eric Joyner <erj@FreeBSD.org>

PR: 273043
Sponsored by: Intel Corporation
Reviewed by: jhibbits@, erj@
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D41426