drm/vc4: dsi: Drop unused i2c include

The driver doesn't make use of any symbol provided by <linux/i2c.h>. So
drop the include.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221219084023.1402282-1-u.kleine-koenig@pengutronix.de