Port to STM32

Augment flash controllers with their instance on STM32

Author: per42

dt-rust.yaml

@@ -44,6 +44,7 @@
       - "nordic,nrf52-flash-controller"
       - "nordic,nrf51-flash-controller"
       - "raspberrypi,pico-flash-controller"
+      - "st,stm32-flash-controller"
       level: 0
   actions:
   - type: instance