drm/mgag200: Use fbdev-shmem

Implement fbdev emulation with fbdev-shmem. Avoids the overhead of
fbdev-generic's additional shadow buffering. No functional changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-13-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_drv.c

@@ -12,7 +12,7 @@
 #include <drm/drm_aperture.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
-#include <drm/drm_fbdev_generic.h>
+#include <drm/drm_fbdev_shmem.h>
 #include <drm/drm_file.h>
 #include <drm/drm_ioctl.h>
 #include <drm/drm_managed.h>
@@ -285,7 +285,7 @@ mgag200_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	 * FIXME: A 24-bit color depth does not work with 24 bpp on
 	 * G200ER. Force 32 bpp.
 	 */
-	drm_fbdev_generic_setup(dev, 32);
+	drm_fbdev_shmem_setup(dev, 32);
 
 	return 0;
 }