iommu/arm-smmu-v3: Clean up bus_set_iommu()

Stop calling bus_set_iommu() since it's now unnecessary, and simplify
the probe failure path accordingly.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/6235f07df013776656a61bb642023ecce07f46cc.1660572783.git.robin.murphy@arm.com


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