drm: flip cirrus driver status to "obsolete".

Also update Kconfig help text, explaining things:

Cirrus is obsolete, the hardware was designed in the 90ies
and can't keep up with todays needs.  More background:
https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/

Better alternatives are:
  - stdvga (DRM_BOCHS, qemu -vga std, default in qemu 2.2+)
  - qxl (DRM_QXL, qemu -vga qxl, works best with spice)
  - virtio (VIRTIO_GPU), qemu -vga virtio)

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 15eadc8..b8e2bbe6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4116,7 +4116,8 @@
 M:	Gerd Hoffmann <kraxel@redhat.com>
 L:	virtualization@lists.linux-foundation.org
 T:	git git://git.kraxel.org/linux drm-qemu
-S:	Odd Fixes
+S:	Obsolete
+W:	https://www.kraxel.org/blog/2014/10/qemu-using-cirrus-considered-harmful/
 F:	drivers/gpu/drm/cirrus/
 
 RADEON and AMDGPU DRM DRIVERS