drm/fsl-dcu: Use GEM DMA fbdev emulation

Use the fbdev emulation that is optimized for DMA helpers. Avoids
possible shadow buffering and makes the code simpler.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230313155138.20584-7-tzimmermann@suse.de

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c

@@ -20,7 +20,7 @@
 
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
-#include <drm/drm_fbdev_generic.h>
+#include <drm/drm_fbdev_dma.h>
 #include <drm/drm_gem_dma_helper.h>
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_module.h>
@@ -333,7 +333,7 @@ static int fsl_dcu_drm_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto put;
 
-	drm_fbdev_generic_setup(drm, legacyfb_depth);
+	drm_fbdev_dma_setup(drm, legacyfb_depth);
 
 	return 0;