drm/i915: Add encoder->post_pll_disable() hooks and move CHV clock buffer disables there

Move the CHV clock buffer disable from chv_disable_pll() to the new
encoder .post_pll_disable() hook. This is more symmetric since the
clock buffer enable happens from the .pre_pll_enable() hook.

We'll have more use for the new hook soon.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak S <deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 8383442..525e457 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -142,6 +142,7 @@
 	void (*mode_set)(struct intel_encoder *intel_encoder);
 	void (*disable)(struct intel_encoder *);
 	void (*post_disable)(struct intel_encoder *);
+	void (*post_pll_disable)(struct intel_encoder *);
 	/* Read out the current hw state of this connector, returning true if
 	 * the encoder is active. If the encoder is enabled it also set the pipe
 	 * it is connected to in the pipe parameter. */