Include what you use: <cutils/bitops.h> for popcount

Test: builds OK
Change-Id: Ie717272df285303a63518f0342e1a4d2f41362c3
diff --git a/media/libaudiohal/impl/StreamPowerLog.h b/media/libaudiohal/impl/StreamPowerLog.h
index 5fd3912..f6a554b 100644
--- a/media/libaudiohal/impl/StreamPowerLog.h
+++ b/media/libaudiohal/impl/StreamPowerLog.h
@@ -19,6 +19,7 @@
 
 #include <audio_utils/clock.h>
 #include <audio_utils/PowerLog.h>
+#include <cutils/bitops.h>
 #include <cutils/properties.h>
 #include <system/audio.h>