drm/i915/pmu: Fix building without CONFIG_PM

As we peek inside struct device to query members guarded by CONFIG_PM,
so must be the code.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: 1fe699e3 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180207160428.17015-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_pmu.c

@@ -415,13 +415,12 @@ static int i915_pmu_event_init(struct perf_event *event)
 	return 0;
 }
 
-static u64 get_rc6(struct drm_i915_private *i915, bool locked)
+static u64 __get_rc6(struct drm_i915_private *i915)
 {
-	unsigned long flags;
 	u64 val;
 
-	if (intel_runtime_pm_get_if_in_use(i915)) {
-		val = intel_rc6_residency_ns(i915, IS_VALLEYVIEW(i915) ?
+	val = intel_rc6_residency_ns(i915,
+				     IS_VALLEYVIEW(i915) ?
 				     VLV_GT_RENDER_RC6 :
 				     GEN6_GT_GFX_RC6);
 
@@ -431,6 +430,17 @@ static u64 get_rc6(struct drm_i915_private *i915, bool locked)
 	if (HAS_RC6pp(i915))
 		val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6pp);
 
+	return val;
+}
+
+static u64 get_rc6(struct drm_i915_private *i915, bool locked)
+{
+#if IS_ENABLED(CONFIG_PM)
+	unsigned long flags;
+	u64 val;
+
+	if (intel_runtime_pm_get_if_in_use(i915)) {
+		val = __get_rc6(i915);
 		intel_runtime_pm_put(i915);
 
 		/*
@@ -487,6 +497,9 @@ static u64 get_rc6(struct drm_i915_private *i915, bool locked)
 	}
 
 	return val;
+#else
+	return __get_rc6(i915);
+#endif
 }
 
 static u64 __i915_pmu_event_read(struct perf_event *event, bool locked)