dfu: avoid memory leak

When dfu_fill_entity fail, need to free dfu to avoid memory leak.

Reported by Coverity:
"
Resource leak (RESOURCE_LEAK)
leaked_storage: Variable dfu going out of scope leaks the storage
it points to.
"
Signed-off-by: NPeng Fan <van.freenix@gmail.com>
Cc: "Łukasz Majewski" <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>

drivers/dfu/dfu.c

@@ -468,8 +468,10 @@ int dfu_config_entities(char *env, char *interface, char *devstr)
 		s = strsep(&env, ";");
 		ret = dfu_fill_entity(&dfu[i], s, alt_num_cnt, interface,
 				      devstr);
-		if (ret)
+		if (ret) {
+			free(dfu);
 			return -1;
+		}
 
 		list_add_tail(&dfu[i].list, &dfu_list);
 		alt_num_cnt++;