MLK-20356-1 common: Fix resource leak in sparse image writting

Fix coverity issue CID 18031: Resource leak (RESOURCE_LEAK)
leaked_storage: Variable fill_buf going out of scope leaks the storage it points to

Should free the fill_buf before function return.

Signed-off-by: Ye Li <ye.li@nxp.com>

common/image-sparse.c

@@ -200,6 +200,7 @@ void write_sparse_image(
 				    __func__);
 				fastboot_fail(
 				    "Request would exceed partition size!");
+				free(fill_buf);
 				return;
 			}