Nitro A0 has a hardware bug in the rx path.  The workaround is to create
a special COS context as a path for non-RSS (non-IP) packets.  Without this
workaround, the chip may stall when receiving RSS and non-RSS packets.

Add infrastructure to allow 2 contexts (RSS and CoS) per VNIC.  Allocate
and configure the CoS context for Nitro A0.
Signed-off-by: Prashant Sreedharan <prashant.sreedharan@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>