If you don't want the legacy drivers, then lets get rid of all the
legacy codepaths from the core module.

This drop the size of drm.ko for me by about 10%.
 380515    7422    4192  392129   5fbc1 ../../drm-next-build/drivers/gpu/drm/drm.ko
 351736	   7298	   4192	 363226	  58ada	../../drm-next-build/drivers/gpu/drm/drm.ko

v2: drop drm_lock as well, fix some DMA->DRM typos
v3: avoid ifdefs in mainline code
v4: rework ioctl defs
v4.1: fix nouveau Kconfig
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>