usb: serial: kobil_sct: fix compile warning:

Fix the following compile warning:

drivers/usb/serial/kobil_sct.c: In function ‘__check_debug’:
drivers/usb/serial/kobil_sct.c:719:1: warning: return from incompatible
pointer type [enabled by default]
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/kobil_sct.c

@@ -38,7 +38,7 @@
 #include <linux/ioctl.h>
 #include "kobil_sct.h"
 
-static int debug;
+static bool debug;
 
 /* Version Information */
 #define DRIVER_VERSION "21/05/2004"