drm/fb-helper: Move out modeset config code

No functional changes, just moving code as-is and fixing includes.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190608152657.36613-4-noralf@tronnes.org


Patch-mainline: 20190608152657.36613-4-noralf@tronnes.org @ 08/06/19, 03:26 p.m.
[quic_stalekar@quicinc.com:
1. drop changes for drm_fb_helper.c, since it is not require.
2. missing inclusion of header file due to conflict.
3. add structure definition to resolve compilation issue.
4. replace drm_connector_get with drm_connector_reference and
drm_connector_put with drm_connector_unreference.
5. add minor changes to resolve compilation.].

Change-Id: If248f45f37f7e449288e39d55ebd64bcc4adebfb
Signed-off-by: Shubham Talekar <quic_stalekar@quicinc.com>