gcc-plugins: structleak: remove unneeded variable 'ret'

Fix the following coccicheck warning:

scripts/gcc-plugins/structleak_plugin.c:177:14-17: Unneeded variable:
"ret". Return "0" on line 207
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200418070505.10715-1-yanaijie@huawei.com

scripts/gcc-plugins/structleak_plugin.c

@@ -170,7 +170,6 @@ static void initialize(tree var)
 static unsigned int structleak_execute(void)
 {
 	basic_block bb;
-	unsigned int ret = 0;
 	tree var;
 	unsigned int i;
 
@@ -200,7 +199,7 @@ static unsigned int structleak_execute(void)
 			initialize(var);
 	}
 
-	return ret;
+	return 0;
 }
 
 #define PASS_NAME structleak