sunxi: video: HDMI: split VSYNC and HSYNC polarity settings
These are actually different bits, and since some monitors (Benq BL2420PT)
have modes with different HSYNC and VSYNC polarity, we should set them
independently
Tested on Pine64-LTS with Benq BL2420PT monitor.
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com> Reviewed-by: Anatolij Gustschin <agust@denx.de> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Reviewed-by: Jagan Teki <jagan@openedev.com>