net/octeontx2: fix loopback config return for VF
net/octeontx2: fix loopback config return for VF

loopback mode is not supported for VFs so returning error if
VF is being configured with loopback mode.

Fixes: 920717e4d8ba ("net/octeontx2: add device start operation")
Cc: stable@dpdk.org

Signed-off-by: Sunil Kumar Kori <bdee174bc83e2fb76d979ba14c67b948a0d67de5@marvell.com>
Acked-by: Jerin Jacob <352c4d4f9291b869992ddb67daa45ddc149fed30@marvell.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk