drm: Extract drm_mode_config.[hc]

And shuffle the kernel-doc structure a bit since drm_crtc.[hc] now
only contains CRTC-related functions and structures.

v2:
- rebase onto drm-misc
- don't forget to move drm_mode_config_cleanup.
- move 2 internal decls under the right heading (Chris)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/Makefile

@@ -16,7 +16,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_framebuffer.o drm_connector.o drm_blend.o \
 		drm_encoder.o drm_mode_object.o drm_property.o \
 		drm_plane.o drm_color_mgmt.o drm_print.o \
-		drm_dumb_buffers.o
+		drm_dumb_buffers.o drm_mode_config.o
 
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o