drm: Extract drm_atomic_state_helper.[hc]

We already have a separate overview doc for this, makes sense to
untangle it from the overall atomic helpers.

v2: Rebase

v3: Rebase more.

Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181004202446.22905-4-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index bc6a16a3..576ba98 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -36,7 +36,8 @@
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
 		drm_kms_helper_common.o drm_dp_dual_mode_helper.o \
 		drm_simple_kms_helper.o drm_modeset_helper.o \
-		drm_scdc_helper.o drm_gem_framebuffer_helper.o
+		drm_scdc_helper.o drm_gem_framebuffer_helper.o \
+		drm_atomic_state_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o