drm/i915: Remove dead code from runtime resume handler

Remove the SNB PCH refclock init call from the runtime resume handler.
I don't think it was actually needed even when we had SNB runtime PM,
and if definitely isn't needed ever since SNB runtime PM was nuked in
commit d4c5636 ("drm/i915: Remove runtime PM for SNB").

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170601183043.28543-1-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -2470,9 +2470,6 @@ static int intel_runtime_resume(struct device *kdev)
 
 	intel_guc_resume(dev_priv);
 
-	if (IS_GEN6(dev_priv))
-		intel_init_pch_refclk(dev_priv);
-
 	if (IS_GEN9_LP(dev_priv)) {
 		bxt_disable_dc9(dev_priv);
 		bxt_display_core_init(dev_priv, true);