drm/mediatek: dsi: fix error codes in mtk_dsi_host_transfer()

drm/mediatek: dsi: fix error codes in mtk_dsi_host_transfer()

There is a type bug because the return statement:

        return ret < 0 ? ret : recv_cnt;

The issue is that ret is an int, recv_cnt is a u32 and the function
returns ssize_t, which is a signed long.  The way that the type promotion
works is that the negative error codes are first cast to u32 and then
to signed long.  The error codes end up being positive instead of
negative and the callers treat them as success.

Fixes: 81cc7e51c4f1 ("drm/mediatek: Allow commands to be sent during video mode")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202412210801.iADw0oIH-lkp@intel.com/
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/b754a408-4f39-4e37-b52d-7706c132e27f@stanley.mountain/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>