drm/i915: enable and disable PIPE_CLK_SEL at the right time

Previously we were enabling it at mode_set but never disabling. Let's
follow the mode set sequence.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_drv.h

@@ -584,5 +584,7 @@ extern void intel_ddi_pll_init(struct drm_device *dev);
 extern void intel_ddi_enable_pipe_func(struct drm_crtc *crtc);
 extern void intel_ddi_disable_pipe_func(struct drm_i915_private *dev_priv,
 					enum pipe pipe);
+extern void intel_ddi_enable_pipe_clock(struct intel_crtc *intel_crtc);
+extern void intel_ddi_disable_pipe_clock(struct intel_crtc *intel_crtc);
 
 #endif /* __INTEL_DRV_H__ */