drm/edid: Add 6 bpc quirk for BOE panel in HP Pavilion 15-n233sl

drm/edid: Add 6 bpc quirk for BOE panel in HP Pavilion 15-n233sl

There's another panel that reports "DFP 1.x compliant TMDS" but it
supports 6bpc instead of 8 bpc.

Apply 6 bpc quirk for the panel to fix it.

BugLink: https://bugs.launchpad.net/bugs/1794387
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181002152911.4370-1-kai.heng.feng@canonical.com