iommu/arm-smmu: Don't register fwnode for legacy binding

iommu/arm-smmu: Don't register fwnode for legacy binding

When using the legacy binding we bypass the of_xlate mechanism, so avoid
registering the instance fwnodes which act as keys for that. This will
help __iommu_probe_device() to retrieve the registered ops the same way
as for x86 etc. when no fwspec has previously been set up by of_xlate.

Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/18b0f812a42a74dd6924aea24e68ab409d6e1b52.1700589539.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>