This patch simplifies the adding and removing VLANs from
VFTA/VLVF/VLVFB registers. The logic to determine the registers to use
has been simplified to (vid / 32) and (1 - vid / 32). Many conditional
paths and checks are no longer needed with this patch.
Signed-off-by: Beilei Xing <beilei.xing@intel.com>