bnxt_en: Use bnxt_cp_ring_info struct pointer as parameter for RX path.

In the RX code path, we current use the bnxt_napi struct pointer to
identify the associated RX/CP rings.  Change it to use the struct
bnxt_cp_ring_info pointer instead since there are now up to 2
CP rings per MSIX.

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