iommu/amd: Remove a few unused exports

Remove exports for functions that are only used in the AMD IOMMU driver
itself, or the also always builtin perf events support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210402143312.372386-4-hch@lst.de


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