qcacmn: include the qdf_event header file when using qdf events

Fix compilation error since qdf_event is used without including
the appropriate header file.

Change-Id: Iecc2f4080f8cb699ada4892dd431d68df4a080ca
CRs-Fixed: 994652

htc/htc_internal.h

@@ -37,6 +37,7 @@ extern "C" {
 #include <qdf_lock.h>
 #include <qdf_timer.h>
 #include <qdf_atomic.h>
+#include <qdf_event.h>
 #include "hif.h"
 #include <htc.h>
 #include "htc_api.h"