iommu/io-pgtable-arm: Fix cfg reading in arm_lpae_concat_mandatory()

iommu/io-pgtable-arm: Fix cfg reading in arm_lpae_concat_mandatory()

The newly introduced arm_lpae_concat_mandatory() function reads the
ias/oas fields from the 'io_pgtable_cfg' copy embedded inside the
'arm_lpae_io_pgtable' structure. However, this copy is not set until
later in alloc_io_pgtable_ops() after the alloc() function has been
called.

Use the address sizes passed in the 'io_pgtable_cfg' structure when
deciding whether or not to concatenate the PGD.

Fixes: 4dcac8407fe1 ("iommu/io-pgtable-arm: Fix stage-2 concatenation with 16K")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Link: https://lore.kernel.org/r/20241215200412.561400-1-smostafa@google.com
Signed-off-by: Will Deacon <will@kernel.org>