target/cortex_a: fix memory leak on watchpoints

The memory allocated to hold the watchpoints is not freed at
OpenOCD exit.

Free the watchpoint memory at OpenOCD exit.

Change-Id: I518c9ce0dc901cde2913d752e3154734f878b854
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6210
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/target/cortex_a.c

@@ -3181,6 +3181,7 @@ static void cortex_a_deinit_target(struct target *target)
 					dscr & ~DSCR_HALT_DBG_MODE);
 	}
 
+	free(cortex_a->wrp_list);
 	free(cortex_a->brp_list);
 	arm_free_reg_cache(dpm->arm);
 	free(dpm->dbp);