iommu: Tidy up Kconfig for SoC IOMMUs

Wacky COMPILE_TEST dependencies based on who used to define
dev_archdata.iommu can go.

Dependencies on ARM or ARM64 already implied by the ARCH_* platform
selection can go.

The entire IOMMU_SUPPORT menu already depends on MMU, so those can go.

IOMMU_DMA is for the architecture's DMA API implementation to choose,
and its interface to IOMMU drivers is properly stubbed out if disabled,
so dependencies on or selections of that can go (AMD_IOMMU is the
current exception since the x86 drivers have to provide their own entire
dma_map_ops implementation).

Since commit ed6ccf10

 ("dma-mapping: properly stub out the DMA API
for !CONFIG_HAS_DMA"), drivers which simply use the dma-mapping API
should not need to depend on HAS_DMA, so those can go.

And a long-dead option for code removed from the MSM driver 4 years ago
can also go.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/7fb9c74dc6bd12a4619ca44c92408e91352f1be0.1593791968.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>