printer yin UPDATE print extension instances (#2180)

Co-authored-by: zhangtao 00621101 <zhangtao387@huawei.com>
diff --git a/src/printer_yin.c b/src/printer_yin.c
index a16db1f..a7f5e0a 100644
--- a/src/printer_yin.c
+++ b/src/printer_yin.c
@@ -111,6 +111,8 @@
         } else {
             ypr_open(pctx, stmt->stmt, lys_stmt_arg(stmt->kw), stmt->arg, flag);
         }
+    } else if (stmt->kw == LY_STMT_EXTENSION_INSTANCE) {
+        ypr_open(pctx, stmt->stmt, (stmt->arg && stmt->arg[0]) ? lys_stmt_arg(LY_STMT_VALUE) : NULL, stmt->arg, flag);
     }
 
     if (stmt->child) {