qcacld-3.0: Fix -Wmissing-prototypes in wlan_hdd_debugfs

We want to enable the compiler's -Wmissing-prototypes switch, but
there is existing code that is generating warnings. Fix all warnings
in wlan_hdd_debugfs.

Change-Id: I6ebadd731e4d92a63025567ef75bc939faa0e546
CRs-Fixed: 1074336

core/hdd/src/wlan_hdd_debugfs.c

@@ -39,6 +39,7 @@
 #define HDD_DISALLOW_LEGACY_HDDLOG 1
 
 #include <wlan_hdd_includes.h>
+#include <wlan_hdd_debugfs.h>
 #include <wlan_hdd_wowl.h>
 #include <cds_sched.h>