iommu/amd: Remove unused declarations

Commit aafd8ba0 ("iommu/amd: Implement add_device and remove_device")
removed the implementations but left declarations in place. Remove it.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230814135502.4808-1-yuehaibing@huawei.com


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