iommu/arm-smmu-v3: Fix pgsize_bit for sva domains

UBSan caught a bug with IOMMU SVA domains, where the reported exponent
value in __arm_smmu_tlb_inv_range() was >= 64.
__arm_smmu_tlb_inv_range() uses the domain's pgsize_bitmap to compute
the number of pages to invalidate and the invalidation range. Currently
arm_smmu_sva_domain_alloc() does not setup the iommu domain's
pgsize_bitmap. This leads to __ffs() on the value returning 64 and that
leads to undefined behaviour w.r.t. shift operations

Fix this by initializing the iommu_domain's pgsize_bitmap to PAGE_SIZE.
Effectively the code needs to use the smallest page size for
invalidation

Cc: stable@vger.kernel.org
Fixes: eb6c9764 ("iommu/arm-smmu-v3: Avoid constructing invalid range commands")
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Balbir Singh <balbirs@nvidia.com>

Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250412002354.3071449-1-balbirs@nvidia.com


Signed-off-by: Will Deacon <will@kernel.org>