When built as a module, modprobe followed by rmmod can fail because
DMA was still active. So to fix this, DMA needs to be disabled during
module exit.

This change disables DMA during modules exit and change the ISH PCI
device status to D3.
Signed-off-by: Even Xu <even.xu@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>