drm/i915: turn some bogus kernel-doc comments to normal comments

Apparently accidental or misplaced /** kernel-doc comments, confusing
the tool. Turn them to normal comments.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1453101588-18008-2-git-send-email-jani.nikula@intel.com
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 6b2b3e3..7e6e700 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4138,7 +4138,7 @@
 		dev_priv->display.update_wm(crtc);
 }
 
-/**
+/*
  * Lock protecting IPS related data structures
  */
 DEFINE_SPINLOCK(mchdev_lock);