vfio/fsl-mc: return -EFAULT if copy_to_user() fails

The copy_to_user() function returns the number of bytes remaining to be
copied, but this code should return -EFAULT.

Fixes: df747bcd ("vfio/fsl-mc: Implement VFIO_DEVICE_GET_REGION_INFO ioctl call")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Diana Craciun <diana.craciun@oss.nxp.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>