drm/i915: Remove skl dc6 enable/disable functions

One is outright unused, other can be made static.

Drive-by cleanup while accidentally reading dc code.

Cc: Imre Deak <imre.deak@intel.com>
Acked-by: Imre Deak <imre.deak@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180417100225.12286-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/intel_drv.h

@@ -1580,8 +1580,6 @@ void bxt_enable_dc9(struct drm_i915_private *dev_priv);
 void bxt_disable_dc9(struct drm_i915_private *dev_priv);
 void gen9_enable_dc5(struct drm_i915_private *dev_priv);
 unsigned int skl_cdclk_get_vco(unsigned int freq);
-void skl_enable_dc6(struct drm_i915_private *dev_priv);
-void skl_disable_dc6(struct drm_i915_private *dev_priv);
 void intel_dp_get_m_n(struct intel_crtc *crtc,
 		      struct intel_crtc_state *pipe_config);
 void intel_dp_set_m_n(struct intel_crtc *crtc, enum link_m_n_set m_n);

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -635,7 +635,7 @@ static void assert_can_enable_dc6(struct drm_i915_private *dev_priv)
 	assert_csr_loaded(dev_priv);
 }
 
-void skl_enable_dc6(struct drm_i915_private *dev_priv)
+static void skl_enable_dc6(struct drm_i915_private *dev_priv)
 {
 	assert_can_enable_dc6(dev_priv);
 
@@ -649,13 +649,6 @@ void skl_enable_dc6(struct drm_i915_private *dev_priv)
 	gen9_set_dc_state(dev_priv, DC_STATE_EN_UPTO_DC6);
 }
 
-void skl_disable_dc6(struct drm_i915_private *dev_priv)
-{
-	DRM_DEBUG_KMS("Disabling DC6\n");
-
-	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
-}
-
 static void hsw_power_well_sync_hw(struct drm_i915_private *dev_priv,
 				   struct i915_power_well *power_well)
 {