jtag: parport: avoid freeing read-only memory section

If command parport_cable is not executed, parport_cable points to
const char array in read-only memory as default. On exit free()
will try to free this read-only memory. This patch uses strdup to
allocate memory when defining default setting.

Change-Id: I290e707ac6a37e9dc1b45c85ca51d8bd6aac6761
Signed-off-by: Stefan Mahr <stefan.mahr@sphairon.com>
Reviewed-on: http://openocd.zylin.com/1223


Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/jtag/drivers/parport.c

@@ -268,8 +268,8 @@ static int parport_init(void)
 
 	cur_cable = cables;
 
-	if ((parport_cable == NULL) || (parport_cable[0] == 0)) {
-		parport_cable = "wiggler";
+	if (parport_cable == NULL) {
+		parport_cable = strdup("wiggler");
 		LOG_WARNING("No parport cable specified, using default 'wiggler'");
 	}