drm/msm/adreno: Drop fictional address_space_size

Really the only purpose of this was to limit the address space size to
4GB to avoid 32b rollover problems in 64b pointer math in older sqe fw.
So replace the address_space_size with a quirk limiting the address
space to 4GB.  In all other cases, use the SMMU input address size (IAS)
to determine the address space size.

v2: Properly account for vm_start

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/649467/