iommu/arm-smmu-v3: Add an inline arm_smmu_domain_free()

iommu/arm-smmu-v3: Add an inline arm_smmu_domain_free()

There will be a bit more things to free than smmu_domain itself. So keep a
simple inline function in the header to share aross files.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Balbir Singh <balbirs@nvidia.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Will Deacon <will@kernel.org>