Add stm32 flash + bootloader support

* Add flash drivers for L0, L1, L4, WB and WL. Not tested for WB, but
should be similar to WL.
* Add embassy-boot-stm32 for bootloading on STM32.
* Add flash examples and bootloader examples
* Update stm32-data

examples/boot/nrf/README.md

@@ -0,0 +1,31 @@
+# Examples using bootloader
+
+Example for nRF52 demonstrating the bootloader. The example consists of application binaries, 'a'
+which allows you to press a button to start the DFU process, and 'b' which is the updated
+application.
+
+
+## Prerequisites
+
+* `cargo-binutils`
+* `cargo-flash`
+* `embassy-boot-nrf`
+
+## Usage
+
+
+
+```
+# Flash bootloader
+cargo flash --manifest-path ../../embassy-boot/nrf/Cargo.toml --release --features embassy-nrf/nrf52840 --chip nRF52840_xxAA
+# Build 'b'
+cargo build --release --features embassy-nrf/nrf52840 --bin b
+# Generate binary for 'b'
+cargo objcopy --release --features embassy-nrf/nrf52840 --bin b -- -O binary b.bin
+```
+
+# Flash `a` (which includes b.bin)
+
+```
+cargo flash --release --features embassy-nrf/nrf52840 --bin a --chip nRF52840_xxAA
+```