iommu/core: Remove global iommu_ops and register_iommu

With all IOMMU drivers being converted to bus_set_iommu the
global iommu_ops are no longer required. The same is true
for the deprecated register_iommu function.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

diff --cc drivers/iommu/iommu.c
Simple merge

diff --cc include/linux/iommu.h
Simple merge