octeontx2-pf: mcs: Support VLAN in clear text

Detect whether macsec secy is running on top of VLAN
which implies transmitting VLAN tag in clear text before
macsec SecTag. In this case configure hardware to insert
SecTag after VLAN tag.

Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>