drm/cirrus: make fbdev support really optional

Currently enabling QEMU Cirrus 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: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468586897-32298-6-git-send-email-tjakobi@math.uni-bielefeld.de

drivers/gpu/drm/cirrus/Kconfig

 config DRM_CIRRUS_QEMU
 	tristate "Cirrus driver for QEMU emulated device"
 	depends on DRM && PCI
-	select FB_SYS_FILLRECT
-	select FB_SYS_COPYAREA
-	select FB_SYS_IMAGEBLIT
 	select DRM_KMS_HELPER
-	select DRM_KMS_FB_HELPER
 	select DRM_TTM
 	help
 	 This is a KMS driver for emulated cirrus device in qemu.