drm/tiny/st7586: Use fbdev-dma

Implement fbdev emulation with fbdev-dma. Fbdev-dma now supports
damage handling, which is required by st7586. Avoids the overhead of
fbdev-generic's additional shadow buffering. No functional changes.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Cc: David Lechner <[e-mail]>
Acked-by: David Lechner <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/tiny/st7586.c

···
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_fb_dma_helper.h>
-#include <drm/drm_fbdev_generic.h>
+#include <drm/drm_fbdev_dma.h>
 #include <drm/drm_format_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_atomic_helper.h>
···
 
 	spi_set_drvdata(spi, drm);
 
-	drm_fbdev_generic_setup(drm, 0);
+	drm_fbdev_dma_setup(drm, 0);
 
 	return 0;
 }