UPSTREAM: arm64: mm: check at build time that PAGE_OFFSET divides the VA space evenly

Commit 8439e62a ("arm64: mm: use bit ops rather than arithmetic in
pa/va translations") changed the boundary check against PAGE_OFFSET from
an arithmetic comparison to a bit test. This means we now silently assume
that PAGE_OFFSET is a power of 2 that divides the kernel virtual address
space into two equal halves. So make that assumption explicit.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Bug: 30369029
Patchset: kaslr-arm64-4.4

(cherry picked from commit 6d2aa549)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: I8c3bc8cdb7d7f7dea092fd1a208b04583a141054