drm/panel: sofef00: Use 16-bit brightness function

These panels communicate 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 doing special processing
of the brightness values.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Tested-by: Caleb Connolly <caleb@connolly.tech>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230116224909.23884-3-mailingradian@gmail.com