drm/rockchip: lvds: Create an RK3288 specific probe function

The probe function is highly adapted to the RK3288 specificities, move
all specific bits into an "rk3288_probe" function, also part of the
platform data.

The goal is to ease the addition of new flavors of Rockchip LVDS IPs.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20191224143900.23567-7-miquel.raynal@bootlin.com