drm/i915: extract ums suspend/resume into i915_ums.c

Similarly to how i915_dma.c is shaping up to be the dungeon hole for
all things supporting dri1, create a new one to hide all the crazy
things which are only really useful for ums support. Biggest part is
the register suspend/resume support.

Unfortunately a lot of it is still intermingled with bits and pieces
we might still need, so needs more analysis and needs to stay in
i915_suspend.c for now.
Reviewed-by: Imre Deak <imre.deak@intel.com>

v2: s/modeset_reg/display_reg/ as suggested by Imre, to avoid
confusion between the kernel modeset code and display save/restore to
support ums.

v3: Fixup alphabetical order in the Makefile, spotted by Chris Wilson.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/Makefile

@@ -16,6 +16,7 @@ i915-y := i915_drv.o i915_dma.o i915_irq.o \
 	  i915_gem_tiling.o \
 	  i915_sysfs.o \
 	  i915_trace_points.o \
+	  i915_ums.o \
 	  intel_display.o \
 	  intel_crt.o \
 	  intel_lvds.o \

drivers/gpu/drm/i915/i915_drv.h

@@ -1730,9 +1730,9 @@ void i915_debugfs_cleanup(struct drm_minor *minor);
 extern int i915_save_state(struct drm_device *dev);
 extern int i915_restore_state(struct drm_device *dev);
 
-/* i915_suspend.c */
-extern int i915_save_state(struct drm_device *dev);
-extern int i915_restore_state(struct drm_device *dev);
+/* i915_ums.c */
+void i915_save_display_reg(struct drm_device *dev);
+void i915_restore_display_reg(struct drm_device *dev);
 
 /* i915_sysfs.c */
 void i915_setup_sysfs(struct drm_device *dev_priv);