We currently use a single data buffer shared between all admin queue
descriptors.  This works for the physical function driver since we
have at most one command in progress and only a single event (which
does not use a data buffer).

The communication path between the physical and virtual function
drivers uses the event data buffer, and there is no way to prevent a
solicited event (i.e. a response to a request) from being overwritten
by an unsolicited event (e.g. a link status change).

Provide individual data buffers for each admin event queue descriptor
(and for each admin command queue descriptor, for the sake of
consistency).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

The register map for the virtual functions appears to have been
constructed using a random number generator.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

The physical function driver does not allow the virtual function to
request that VLAN tags are left unstripped.  Extract and use the VLAN
tag from the receive descriptor if present.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>