drm-misc-fixes for v4.19:
- Fix use of freed memory in drm_mode_setcrtc.
- Reject pixel format changing requests in fb helper.
- Add 6 bpc quirk for HP Pavilion 15-n233sl
- Fix VSDB yCBCr420 Deep Color mode bit definitions

Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/647fe5d0-4ec5-57cc-9f23-a4836b29e278@linux.intel.com