drm/panel: vtdr6130: Use 16-bit brightness function

This panel communicates brightness in big endian. This is not a quirk of
the panels themselves, but rather, a part of the MIPI standard. Use the
new mipi_dsi_dcs_set_display_brightness_large() function that properly
handles 16-bit brightness instead of bypassing the brightness functions
entirely.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-MTP
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230116224909.23884-4-mailingradian@gmail.com