be2net: do not use frag index in the RX-compl entry

Instead, use the tail of the RXQ to pick the associated RXQ entry

This fix is required in preparation for supporting RXQ lengths greater than 1K.
For such queues, the frag index in the RX-compl entry is not valid as it is only a 10 bit entry not capable of addressing RXQs longer than 1K.

Signed-off-by: Suresh Reddy <suresh.reddy@emulex.com>
Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>