Apply the "panel orientation" drm connector prop to the primary plane so
that fbcon and fbdev using userspace programs display the right way up.

Changes in v3:
-Use a rotation member in struct drm_fb_helper_crtc and set that from
 drm_setup_crtcs instead of looping over all crtc's to find the right one
 later
-Since we now no longer look at rotation quirks directly in the fbcon
 code, set fb_info.fbcon_rotate_hint when the panel is not mounted upright
 and we cannot use hardware rotation

Changes in v4:
-Make drm_fb_helper_init() init drm_fb_helper_crtc.rotation to
 DRM_MODE_ROTATE_0 for all crtcs, so that we do not end up setting the
 plane_state's rotation to an invalid value for disabled crtcs
 (caught by Fi.CI)

Changes in v5:
-Only use hardware (crtc primary plane) rotation for DRM_ROTATE_180,
 90 / 270 degree rotation requires special handling which we lack atm
-Add a TODO comment for 90 / 270 degree hardware rotation
-Add some comments to better document the default case when mapping
 sw_rotations to fbcon_rotate_hints

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=94894Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171125193553.23986-5-hdegoede@redhat.com