UPSTREAM: drm/rockchip: inno_hdmi: fix an error code

UPSTREAM: drm/rockchip: inno_hdmi: fix an error code

We were accidentally returning PTR_ERR(NULL) which means success when we
wanted to return a negative error code.

Change-Id: Ia56827712eeaafef93ce433c0e05b95534784e30
Fixes: 412d4ae6b7a5 ('drm/rockchip: hdmi: add Innosilicon HDMI support')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Yakir Yang <ykk@rock-chips.com>
(cherry picked from git.kernel.org next/linux-next.git master
 commit 2743becb3338cf012dbe7b70c6c39bbac81cc101)