iommu/arm-smmu: Clean up bus_set_iommu()

Stop calling bus_set_iommu() since it's now unnecessary. With device
probes now replayed for every IOMMU instance registration, the whole
sorry ordering workaround for legacy DT bindings goes too, hooray!

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/f7aaad3e479a78623a6942ed46937249168b55bd.1660572783.git.robin.murphy@arm.com


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