drm/rockchip: inno-hdmi: Fix video timing HSYNC/VSYNC polarity setting for rk3036

The HSYNC/VSYNC polarity of rk3036 HDMI are controlled by GRF.
Without the polarity configuration in GRF, it can be observed
from the HDMI protocol analyzer that the H/V front/back timing
output by RK3036 HDMI are currently not in line with the specifications.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Tested-by: Heiko Stuebner <heiko@sntech.de> #rk3036-kylin
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20250422070455.432666-5-andyshrk@163.com