drm/i915: Refactor save/restore code

We move the display-specific code into it's own functions, called
from the general GPU state save/restore functions. This will be needed
later by the GPU reset code.

Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/gpu/drm/i915/i915_drv.h

@@ -597,6 +597,8 @@ extern int i915_max_ioctl;
 extern unsigned int i915_fbpercrtc;
 extern unsigned int i915_powersave;
 
+extern void i915_save_display(struct drm_device *dev);
+extern void i915_restore_display(struct drm_device *dev);
 extern int i915_master_create(struct drm_device *dev, struct drm_master *master);
 extern void i915_master_destroy(struct drm_device *dev, struct drm_master *master);