Add a more optimized hardware GRO function to setup the SKB on 57500
chips.  Some workaround code is no longer needed on 57500 chips and
the pseudo checksum is also calculated in hardware, so no need to
do the software pseudo checksum in the driver.
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>