ixgbe: Preserve the full VF RSS domain in the shared RETA

The 82599 and X540 share the global RSS redirection table between the
PF and its VFs. Programming that table from the PF queue count
prevents a VF from using queue indices absent from the PF layout. A
one-queue PF consequently directs every flow for a two- or four-queue
VF to queue zero.

Program at least four queue indices while SR-IOV is active. Each pool
PSRTYPE.RQPL field masks the shared table to the queue subset available
to that function, so the PF can continue using fewer queues.

MFC after: 2 weeks