rtl8192cu: fix build error (vmalloc/vfree undefined)

On the ARM system, a build fails due to missing include.
Signed-off-by: NWilly Tarreau <w@1wt.eu>
Signed-off-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/rtl8192cu/sw.c

@@ -40,7 +40,7 @@
 #include "trx.h"
 #include "led.h"
 #include "hw.h"
-
+#include <linux/vmalloc.h>
 
 MODULE_AUTHOR("Georgia		<georgia@realtek.com>");
 MODULE_AUTHOR("Ziv Huang	<ziv_huang@realtek.com>");