bnxt: rename bnxt_rx_pages to bnxt_rx_agg_pages_skb

Clarify that this is reading buffers from the aggregation ring.

Signed-off-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>