ath5k: add missing include for debug code

Needed for calling vmalloc()/vfree()
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/debug.c

@@ -65,6 +65,7 @@
 
 #include <linux/seq_file.h>
 #include <linux/list.h>
+#include <linux/vmalloc.h>
 #include "debug.h"
 #include "ath5k.h"
 #include "reg.h"