drm/i915: Turn off hsync and vsync on ADPA when disabling crt

According to PRM we need to disable hsync and vsync even though ADPA is
disabled. The previous code did infact do the opposite so we fix it.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56359
Tested-by: max <manikulin@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>