gpu: host1x: Make mapped field of push buffers void *

This reduces the amount of casting that needs to be done to get rid of
annoying warnings on 64-bit builds.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/host1x/cdma.c
Simple merge

diff --cc drivers/gpu/host1x/cdma.h
Simple merge

diff --cc drivers/gpu/host1x/hw/cdma_hw.c
Simple merge