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

@@ -12060,6 +12060,7 @@
             "FLASH",
             "MPU"
         ],
+        "device_name": "STM32WB55RGVx",
         "features": [
             "BLE"
         ],
@@ -14176,4 +14177,4 @@
         "version": "1",
         "public": false
     }
-}
+}