iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

iommu/arm-smmu: fix null-pointer dereference in arm_smmu_add_device

Commit c54451a "iommu/arm-smmu: Fix the error path in arm_smmu_add_device"
removed fwspec assignment in legacy_binding path as redundant which is
wrong. It needs to be updated after fwspec initialisation in
arm_smmu_register_legacy_master() as it is dereferenced later. Without
this there is a NULL-pointer dereference panic during boot on some hosts.

Signed-off-by: Artem Savkov <[email protected]>
Reviewed-by: Robin Murphy <[email protected]>
Acked-by: Will Deacon <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>