NUCLEO_WB55RG - add device name "STM32WB55RGVx"

Bootloader compilation will require the device to be in place,
it uses that to pick up the CMSIS-pack info from the index.json.

Author: Janne Kiiskila

targets/targets.json

@@ -8470,6 +8470,7 @@
         ],
         "features": ["BLE"],
         "release_versions": ["2", "5"],
+        "device_name": "STM32WB55RGVx",
         "bootloader_supported": false
     },
     "VBLUNO52": {