ice: Add initial support for QinQ

Allow support for S-Tag + C-Tag VLAN traffic by disabling pruning when
there are no 0x8100 VLAN interfaces currently created on top of the PF.
When an 0x8100 VLAN interface is configured, enable pruning and only
support single and double C-Tag VLAN traffic. If all of the 0x8100
interfaces that were created on top of the PF are removed via
ethtool -K <iface> rx-vlan-filter off or via ip tools, then disable
pruning and allow S-Tag + C-Tag traffic again.

Add VLAN 0 filter by default for the PF. This is because a bridge
sets the default_pvid to 1, sends the request down to
ice_vlan_rx_add_vid(), and we never get the request to add VLAN 0 via
the 8021q module which causes all untagged traffic to be dropped.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>