iommu-fixes-v4.13-rc6

Another fix, this time in common IOMMU sysfs code

	- In the conversion from the old iommu sysfs-code to the
	  iommu_device_register interface, I missed to update the
	  release path for the struct device associated with an IOMMU.
	  It freed the 'struct device', which was a pointer before, but
	  is now embedded in another struct. Freeing from the middle of
	  allocated memory had all kinds of nasty side effects when an
	  IOMMU was unplugged. Unfortunatly nobody unplugged and IOMMU
	  until now, so this was not discovered earlier.  The fix is to
	  make the 'struct device' a pointer again.