drm/msm: Fix address space size after refactor.

Previously the address space went from 16M to ~0u, but with the
refactor one of the 'f's was dropped, limiting us to 256MB.
Additionally, the new interface takes a start and size, not start and
end, so we can't just copy and paste.

Fixes regressions in dEQP-VK.memory.allocation.random.*

Fixes: ccac7ce3 ("drm/msm: Refactor address space initialization")
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Rob Clark <robdclark@chromium.org>