hal: Include POSIX thread header

Change-Id: Ib5a85be489a3807a43a992d113fb06c44e96e807
diff --git a/hal/audio_extn/gef.c b/hal/audio_extn/gef.c
index 69b1e41..553f3eb 100644
--- a/hal/audio_extn/gef.c
+++ b/hal/audio_extn/gef.c
@@ -46,6 +46,7 @@
 #include <cutils/properties.h>
 #include "audio_extn.h"
 #include "audio_hw.h"
+#include <pthread.h>
 
 #ifdef DYNAMIC_LOG_ENABLED
 #include <log_xml_parser.h>