drm/i915: Export the generic, not arch specific, intel_update_watermarks()

Rather than export every single architecture specific update_wm, just
export the wrapper around the display vtable.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index da525b6..10dd1b6 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -112,13 +112,13 @@
 	 */
 	if (crtc_w != src_w || crtc_h != src_h) {
 		dev_priv->sprite_scaling_enabled = true;
-		sandybridge_update_wm(dev);
+		intel_update_watermarks(dev);
 		intel_wait_for_vblank(dev, pipe);
 		sprscale = SPRITE_SCALE_ENABLE | (src_w << 16) | src_h;
 	} else {
 		dev_priv->sprite_scaling_enabled = false;
 		/* potentially re-enable LP watermarks */
-		sandybridge_update_wm(dev);
+		intel_update_watermarks(dev);
 	}
 
 	I915_WRITE(SPRSTRIDE(pipe), fb->pitches[0]);