amd-xgbe: VLAN Rx tag stripping fix

When receiving a VLAN packet check to be sure that VLAN
RX CTAG stripping is enabled before indicating that the
tag has been stripped in the packet information data
structure.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>