amd-xgbe: VLAN Tx tag insertion fix

The MAC_VLAN_Incl register (0x0060) must be set to indicate
that the VLAN tag to be inserted comes from a Tx context
descriptor and not the MAC_VLAN_Incl register.  Also, even
though it is the default, explicitly set the type of tag to
be inserted as a CTAG.

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