iommu/amd: Don't set pasid_state->mm to NULL in unbind_pasid

With calling te mmu_notifier_register function we hold a
reference to the mm_struct that needs to be released in
mmu_notifier_unregister. This is true even if the notifier
was already unregistered from exit_mmap and the .release
call-back has already run.

So make sure we call mmu_notifier_unregister unconditionally
in amd_iommu_unbind_pasid.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Oded Gabbay <oded.gabbay@amd.com>
iommu/amd: Remove change_pte mmu_notifier call-back

All calls to this call-back are wrapped with
mmu_notifer_invalidate_range_start()/end(), making this
notifier pretty useless, so remove it.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Oded Gabbay <oded.gabbay@amd.com>
iommu/amd: Fix device_state reference counting

The references to the device state are not dropped
everywhere. This might cause a dead-lock in
amd_iommu_free_device(). Fix it.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Oded Gabbay <oded.gabbay@amd.com>
iommu/amd: Fix 2 typos in comments

amd_iommu_pasid_bind -> amd_iommu_bind_pasid

Signed-off-by: Joerg Roedel <jroedel@suse.de>