net: Disable GRO_HW when generic XDP is installed on a device.

Hardware should not aggregate any packets when generic XDP is installed.

Cc: Ariel Elior <Ariel.Elior@cavium.com>
Cc: everest-linux-l2@cavium.com
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>