drm/i915: make rc6 in sysfs functions conditional

Commit 0136db586c028f71e7cc21cc183064ff0d5919c8 merges rc6 information
into the power group. However, when compiled with CONFIG_PM not set,
modprobing i915 would taint since power_group_name is defined as NULL.

This patch makes these rc6 in sysfs functions conditional upon the
definition of the CONFIG_PM macro to avoid the above-mentioned problem.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=45181
Cc: stable@vger.kernel.org
Tested-by: Kris Karas <bugs-a12@moonlit-rail.com>
Signed-off-by: Hunt Xu <mhuntxu@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_sysfs.c

@@ -32,6 +32,7 @@
 #include "intel_drv.h"
 #include "i915_drv.h"
 
+#ifdef CONFIG_PM
 static u32 calc_residency(struct drm_device *dev, const u32 reg)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -224,3 +225,14 @@ void i915_teardown_sysfs(struct drm_device *dev)
 	device_remove_bin_file(&dev->primary->kdev,  &dpf_attrs);
 	sysfs_unmerge_group(&dev->primary->kdev.kobj, &rc6_attr_group);
 }
+#else
+void i915_setup_sysfs(struct drm_device *dev)
+{
+	return;
+}
+
+void i915_teardown_sysfs(struct drm_device *dev)
+{
+	return;
+}
+#endif /* CONFIG_PM */