After a guest is shutdown, assigned devices are not properly
returned to the pt domain.  This can leave the device using
stale cached IOMMU data, and result in a non-functional
device after it's re-bound to the host driver.  For example,
I see this upon rebinding:

 AMD-Vi: Event logged [IO_PAGE_FAULT device=02:00.0 domain=0x0000 address=0x000000007e2a8000 flags=0x0050]
 AMD-Vi: Event logged [IO_PAGE_FAULT device=02:00.0 domain=0x0000 address=0x000000007e2a8040 flags=0x0050]
 AMD-Vi: Event logged [IO_PAGE_FAULT device=02:00.0 domain=0x0000 address=0x000000007e2a8080 flags=0x0050]
 AMD-Vi: Event logged [IO_PAGE_FAULT device=02:00.0 domain=0x0000 address=0x000000007e2a80c0 flags=0x0050]
 0000:02:00.0: eth2: Detected Hardware Unit Hang:
 ...

The amd_iommu_destroy_domain() function calls do_detach()
which doesn't reattach the pt domain to the device.
Use __detach_device() instead.

Cc: stable@kernel.org
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>