drm: remove i830 driver

This driver is one of the last users of the big kernel
lock, which is going away. All the hardware supported
by this driver also works with the newer i915 driver,
and recent X.org releases only work with that driver
anyway.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>