Fix ESP-WROOM-02 ram size

Author: hotchpotch

boards/esp_wroom_02.json

@@ -14,12 +14,12 @@
   ], 
   "name": "ESP-WROOM-02", 
   "upload": {
-    "maximum_ram_size": 51200, 
+    "maximum_ram_size": 81920, 
     "maximum_size": 4194304, 
     "require_upload_port": true, 
     "resetmethod": "nodemcu", 
     "speed": 115200
   }, 
   "url": "http://www.esp8266.com/wiki/doku.php?id=esp8266-module-family", 
   "vendor": "Espressif"
-}
+}