drm/rockchip: vop2: Fix eDP/HDMI sync polarities

The hsync/vsync polarities were not honoured for the eDP and HDMI ports.
Add the register settings to configure the polarities as requested by the
DRM_MODE_FLAG_PHSYNC/DRM_MODE_FLAG_PVSYNC flags.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Fixes: 604be855 ("drm/rockchip: Add VOP2 driver")
Tested-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220815133942.4051532-1-s.hauer@pengutronix.de