drm: make CONFIG_DRM depend on CONFIG_SHMEM.

This can be removed later when DRM doesn't depend on shmem.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/Kconfig

@@ -6,7 +6,7 @@
 #
 menuconfig DRM
 	tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
-	depends on (AGP || AGP=n) && PCI && !EMULATED_CMPXCHG
+	depends on (AGP || AGP=n) && PCI && !EMULATED_CMPXCHG && SHMEM
 	help
 	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
 	  introduced in XFree86 4.0. If you say Y here, you need to select