cnic: Fix ring setup/shutdown code

Latest bnx2x driver uses different CID for the iSCSI rings, so
we need to pass it in the ring init data.  The rx ring is also
zeroed out to prevent stale DMA addresses from being used after
shutdown.

The same cp local variable redefined inside the else branch is
also eliminated.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>