drm/panel: sitronix-st7789v: avoid hardcoding polarity info

Add polarity information via mode and bus flags, so that they are no
longer hardcoded and forward the information to the DRM stack. This is
required for adding panels with different settings.

Reviewed-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230714013756.1546769-13-sre@kernel.org