Declare struct timespec before first use

Test: builds without warnings
Bug: 32747393
Change-Id: Ie59b1e577771c55ccb264f54ead2df953165da90
diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index 4c938ac..813cade 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -22,6 +22,7 @@
 #include <strings.h>
 #include <sys/cdefs.h>
 #include <sys/types.h>
+#include <time.h>
 
 #include <cutils/bitops.h>