Some x86 clamshell design devices use portrait tablet screens and a display
engine which cannot rotate in hardware, so the firmware just leaves things
as is and we cannot figure out that the display is oriented non upright
from the hardware.

So at least on x86, we need a quirk table for this. This commit adds a DMI
based quirk table which is initially populated with 5 such devices: Asus
T100HA, GPD Pocket, GPD win, I.T.Works TW891 and the VIOS LTH17.

This quirk table will be used by the drm code to let userspace know that
the display is not mounted upright inside the devices case through a new
panel orientation drm-connector property, as well as to tell fbcon to
rotate the console so that it shows the right way up.

Changes in v5:
-Add a kernel-doc comment documenting drm_get_panel_orientation_quirk()
-Remove board_* matches from the dmi-matches for the VIOS LTH17 laptop,
 keeping only the (identical) sys_vendor and product_name matches.
 This is necessary because an older version of the bios has
 board_vendor set to VOIS instead of VIOS

Changes in v6:
-Add reference to added kernel-docs in Documentation/gpu/drm-kms-helpers.rst

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171125193553.23986-3-hdegoede@redhat.com