targets: add serial and serial-port key to JSON files for seeed boards

targets/wioterminal.json

@@ -2,6 +2,7 @@
     "inherits": ["atsamd51p19a"],
     "build-tags": ["wioterminal"],
     "serial": "usb",
+    "serial-port": ["acm:2886:002d", "acm:2886:802d"],
     "flash-1200-bps-reset": "true",
     "flash-method": "msd",
     "msd-volume-name": "Arduino",

targets/xiao.json

@@ -1,6 +1,8 @@
 {
     "inherits": ["atsamd21g18a"],
     "build-tags": ["xiao"],
+    "serial": "usb",
+    "serial-port": ["acm:2886:802f", "acm:2886:002f"],
     "flash-1200-bps-reset": "true",
     "flash-method": "msd",
     "msd-volume-name": "Arduino",