NULL-terminate all pci_device_id tables

NULL-terminating pci_device_id in pch_dma.c and scx200_acb.c
for appying MODULE_DEVICE_TABLE (to publish modalias-es).

Signed-off-by: Dzianis Kahanovich <mahatma@eu.by>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>