drm: make DRI1 drivers depend on BROKEN

The legacy DRI1 drivers expose highly broken interfaces to user-space. No
modern system should enable them, or you will effectively allow user-space
to circumvent most of your kernel security measures. The DRI1 kernel APIs
are simply broken.

User-space can always use vesafb/efifb/simplefb and friends to get working
graphics.

Lets hide the old drivers behind CONFIG_BROKEN. In case they turn out to
be still used (really?), we can easily revert this and figure out a way to
move them out of sight (e.g., moving all DRI1 drivers to
drivers/gpu/dri1/).

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160804080657.9664-2-dh.herrmann@gmail.com

drivers/gpu/drm/Kconfig

@@ -231,6 +231,7 @@ source "drivers/gpu/drm/mediatek/Kconfig"
 menuconfig DRM_LEGACY
 	bool "Enable legacy drivers (DANGEROUS)"
 	depends on DRM
+	depends on BROKEN
 	help
 	  Enable legacy DRI1 drivers. Those drivers expose unsafe and dangerous
 	  APIs to user-space, which can be used to circumvent access