There is a macro for this already in the <drm/drm_mipi_dsi.h> header, use
that instead and delete the custom DSI write macro defined in the driver.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230107191822.3787147-6-javierm@redhat.com