net/qede: enable and disable VLAN filtering

net/qede: enable and disable VLAN filtering

The device doesn't explicitly support enable/disable
of VLAN filtering. However, VLAN filtering takes effect
when a matching VLAN is configured. So in order to
support enable/disable of VLAN filtering, VLAN 0 is
added/removed respectively. A check is added to ensure that
the user removes all the configured VLANs before disabling
VLAN filtering.

Also VLAN offloads shall be enabled by default and
vlan_tci_outer is to set to 0 for Q-in-Q packets.

Fixes: 2ea6f76 ("qede: add core driver")

Signed-off-by: Harish Patil <harish.patil@qlogic.com>