iommu/amd: Move a few prototypes to include/linux/amd-iommu.h

iommu/amd: Move a few prototypes to include/linux/amd-iommu.h

A few functions that were intentended for the perf events support are
currently declared in arch/x86/events/amd/iommu.h, which mens they are
not in scope for the actual function definition.  Also amdkfd has started
using a few of them using externs in a .c file.  End that misery by
moving the prototypes to the proper header.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210402143312.372386-5-hch@lst.de
Signed-off-by: Joerg Roedel <jroedel@suse.de>