vfio: fix ioctl error handling

vfio: fix ioctl error handling

Calling return copy_to_user(...) in an ioctl will not
do the right thing if there's a pagefault:
copy_to_user returns the number of bytes not copied
in this case.

Fix up vfio to do
	return copy_to_user(...)) ?
		-EFAULT : 0;

everywhere.

Cc: [email protected]
Signed-off-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>