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: Peng Fan <van.freenix@gmail.com>
Cc: "Ɓukasz Majewski" <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
diff --git a/drivers/dfu/dfu.c b/drivers/dfu/dfu.c
index 8f5915e..20dfcbb 100644
--- a/drivers/dfu/dfu.c
+++ b/drivers/dfu/dfu.c
@@ -468,8 +468,10 @@
 		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++;