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

Avoid hard-coding the default_mode and supply it from match data. One
additional layer of abstraction has been introduced, which will be
needed for specifying other panel information (e.g. bus flags) in the
next steps.

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/20230714013756.1546769-9-sre@kernel.org