drm/solomon: Do not include <drm/drm_plane_helper.h>

Remove unnecessary include statements for <drm/drm_plane_helper.h>.
The file contains helpers for non-atomic code and should not be
required by most drivers. No functional changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231204090852.1650-6-tzimmermann@suse.de

drivers/gpu/drm/solomon/ssd130x.h

@@ -17,7 +17,6 @@
 #include <drm/drm_crtc.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_encoder.h>
-#include <drm/drm_plane_helper.h>
 
 #include <linux/regmap.h>