bnxt_en: Add function for VF driver to query default VLAN.

The PF can setup a default VLAN for a VF.  The default VLAN tag is
automatically inserted and stripped without the knowledge of the
stack running on the VF.  The VF driver needs to know that default
VLAN is enabled as VLAN acceleration on the RX side is no longer
supported.  Call netdev_update_features() to fix up the VLAN features
as necessary.  Also, VLAN strip mode must be enabled to strip out
the default VLAN tag.

Only allow VF default VLAN to be set if the firmware spec is >= 1.2.1.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>