iommu/amd: Fix amd_iommu_free_device()

put_device_state_wait() doesn't loop on the condition and a spurious
wakeup will have it free the device state even though there might still
be references out to it.

Fix this by using 'normal' wait primitives.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>