add psram flag on RAK11200 board definition (#3887)

boards/wiscore_rak11200.json

@@ -4,7 +4,7 @@
       "ldscript": "esp32_out.ld"
     },
     "core": "esp32",
-    "extra_flags": "-DARDUINO_ESP32_DEV",
+    "extra_flags": ["-DBOARD_HAS_PSRAM", "-DARDUINO_ESP32_DEV"],
     "f_cpu": "240000000L",
     "f_flash": "40000000L",
     "flash_mode": "dio",