drm/radeon|amgpu: Make fbdev emulation optional

Seems to at least compile fine, only change needed was to use
the fb_set_suspend helper.

Cc: alexander.deucher@amd.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1470847958-28465-5-git-send-email-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/radeon/radeon_fb.c b/drivers/gpu/drm/radeon/radeon_fb.c
index 51284e8..568e036 100644
--- a/drivers/gpu/drm/radeon/radeon_fb.c
+++ b/drivers/gpu/drm/radeon/radeon_fb.c
@@ -382,7 +382,7 @@
 void radeon_fbdev_set_suspend(struct radeon_device *rdev, int state)
 {
 	if (rdev->mode_info.rfbdev)
-		fb_set_suspend(rdev->mode_info.rfbdev->helper.fbdev, state);
+		drm_fb_helper_set_suspend(&rdev->mode_info.rfbdev->helper, state);
 }
 
 bool radeon_fbdev_robj_is_fb(struct radeon_device *rdev, struct radeon_bo *robj)