iommu/arm-smmu: allow 42-bit stage-1 output size with 64K pages

The output size of stage-1 is currently limited by the input size of
stage-2, which is further limited by VA_BITS since we make use of the
standard pgd_alloc functions for creating page tables.

This patch ensures that we use VA_BITS instead of a hardcoded '39'
for the stage-1 output size limit.

Change-Id: Ib3db3bffbd4a5f6082b8ad8eeb01cea754ca0f72
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: c44308413b92a555d1501a6c0db9489e288bb81b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>