drm/rockchip: Disarm vop->is_enabled

drm/rockchip: Disarm vop->is_enabled

With atomic helpers there's no need to track the enabled state of a pipe
any more, because atomic helpers track this accurately already.

Just disable the early returns, since the debug checks might be useful.

v2: Don't call drm_helper_disable_unused_functions, it blows up
without this check. At least explains why rockchip still needed this
old legacy-style state tracing - to work around issues from calling
other legacy style functions!

Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Mark yao <mark.yao@rock-chips.com>
Tested-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-18-git-send-email-daniel.vetter@ffwll.ch