drm/rockchip: lvds: move hardware-specific functions together

Reorganize a bit the functions order to clarify the driver and separate
hardware independent and specific functions a bit. This change only moves
functions around, there is no functional change.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
[adapted to recent drm_panel_get_modes() param change ]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20191224143900.23567-9-miquel.raynal@bootlin.com