iommu/arm-smmu: use VA_BITS to determine arm64 virtual address space

With the introduction of the VA_BITS definition for arm64, make use of
it in the driver, allowing up to 42-bits of VA space when configured
with 64k pages.

Change-Id: I2ba9019a2e309dfac91dbc0215c2ae4b5647c919
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 06f983dd571f564bdd3eb2ac4c33002034ea7810
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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