drm/rockchip: vop2: Add platform specific callback

The VOP interface mux, overlay, background delay cycle configuration
of different SOC are much different. Add platform specific callback
ops to let the core driver look cleaner and more refined.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Tested-by: Michael Riesch <michael.riesch@wolfvision.net> # on RK3568
Tested-by: Detlev Casanova <detlev.casanova@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20250218112744.34433-4-andyshrk@163.com