iommu/arm-smmu: Convert to a global static identity domain

Create a global static identity domain with it's own
arm_smmu_attach_dev_identity() that simply calls
arm_smmu_master_install_s2crs() with the identity parameters.

This is done by giving the attach path for identity its own unique
implementation that simply calls arm_smmu_master_install_s2crs().

Remove ARM_SMMU_DOMAIN_BYPASS and all checks of IOMMU_DOMAIN_IDENTITY.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v2-c86cc8c2230e+160bb-smmu_newapi_jgg@nvidia.com
[will: Move duplicated autosuspend logic into a helper function]
Signed-off-by: Will Deacon <will@kernel.org>