Update MTU value based on PTP enable status and reserve eight
bytes in TX path to accommodate VLAN tags.
If PTP is enabled maximum allowed MTU is 9200 otherwise it's 9208.
Fixes: b5dc3140448e ("net/octeontx2: support base PTP")
Cc: stable@dpdk.org
Signed-off-by: Hanumanth Reddy Pothula <hpothula@marvell.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>