drm/rockchip: vop2: set bg dly and prescan dly at vop2_post_config

We need to setup background delay cycle and prescan
delay cycle when a mode is enable to avoid trigger
POST_BUF_EMPTY irq on rk3588.

Note: RK356x has no such requirement.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231211115815.1785131-1-andyshrk@163.com