iommu/amd: Do not call sleep while holding spinlock

Smatch static checker warns:
	drivers/iommu/amd/iommu_v2.c:133 free_device_state()
	warn: sleeping in atomic context

Fixes by storing the list of struct device_state in a temporary
list, and then free the memory after releasing the spinlock.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 9f968fc7

 ("iommu/amd: Improve amd_iommu_v2_exit()")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20220314024321.37411-1-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>