drm/connector: Hookup the new drm_cmdline_mode panel_orientation member (v2)

If the new video=... panel_orientation option is set for a connector, honor
it and setup a matching "panel orientation" property on the connector.

Changes in v2:
-Improve DRM_INFO message to make it clear that the panel_orientation is
 being forced from the commandline

BugLink: https://gitlab.freedesktop.org/plymouth/plymouth/merge_requests/83


Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200105155120.96466-2-hdegoede@redhat.com