Unbreak non-H/W VLAN extraction case.

Unbreak non-H/W VLAN extraction case.
Unlike other GigEs Yukon II always set VLAN bit when it detects VLAN
tagged packet regardless of H/W VLAN processing configuration state.
So it need to check IFCAP_VLAN_HWTAGGING bit to know whether driver
is configured to take advantage of H/W VLAN processing. If H/W VLAN
processing was disabled don't adjust received packet length such that
subsequent validation logic works for software VLAN processing.

Reported by:	bms
Tested by:	bms