drm/msm: fix 32b build warns

Neither of these code-paths apply to older 32b devices, but it is rude
to introduce warnings.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200929001925.2916984-1-robdclark@gmail.com