xen-pciback: also support disabling of bus-mastering and memory-write-invalidate

It's not clear to me why only the enabling operation got handled so
far.

Signed-off-by: Jan Beulich <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: David Vrabel <[email protected]>
1 file changed