drm/ast: make fbdev support really optional

Currently enabling AST Server DRM support automatically pulls
in fbdev dependency. However this dep is unnecessary since
DRM core already handles this for us (DRM_FBDEV_EMULATION).
Signed-off-by: NTobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468586897-32298-20-git-send-email-tjakobi@math.uni-bielefeld.de

drivers/gpu/drm/ast/Kconfig

@@ -2,11 +2,7 @@ config DRM_AST
 	tristate "AST server chips"
 	depends on DRM && PCI
 	select DRM_TTM
-	select FB_SYS_COPYAREA
-	select FB_SYS_FILLRECT
-	select FB_SYS_IMAGEBLIT
 	select DRM_KMS_HELPER
-	select DRM_KMS_FB_HELPER
 	select DRM_TTM
 	help
 	 Say yes for experimental AST GPU driver. Do not enable