qed: Fix populating the invalid stag value in multi function mode.

In multi-function mode, driver receives the stag value (outer vlan)
for a PF from management FW (MFW). If the stag value is negotiated prior to
the driver load, then the stag is not notified to the driver and hence
driver will have the invalid stag value.
The fix is to request the MFW for STAG value during the driver load time.

Fixes: cac6f691 ("qed: Add support for Unified Fabric Port")
Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Tomer Tayar <Tomer.Tayar@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>