stm32/boards/LEGO_HUB_NO7: Add robust update logic to mboot.

Following change in 899592a

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

ports/stm32/boards/LEGO_HUB_NO7/board_init.c

@@ -199,7 +199,14 @@ int board_mboot_get_reset_mode(uint32_t *initial_r0) {
 }
 
 void board_mboot_state_change(int state, uint32_t arg) {
-    if (state == MBOOT_STATE_FSLOAD_END) {
+    if (state == MBOOT_STATE_FSLOAD_START) {
+        // The FS-load update is about to start.  Program the update key and FS-load elements
+        // into the flash so they can be retrieved if there is a power failure during the update.
+        mp_spiflash_erase_block(MBOOT_SPIFLASH_SPIFLASH, SPIFLASH_UPDATE_KEY_ADDR);
+        mp_spiflash_write(MBOOT_SPIFLASH_SPIFLASH, SPIFLASH_UPDATE_KEY_ADDR + 4, ELEM_DATA_SIZE, ELEM_DATA_START);
+        uint32_t key = SPIFLASH_UPDATE_KEY_VALUE;
+        mp_spiflash_write(MBOOT_SPIFLASH_SPIFLASH, SPIFLASH_UPDATE_KEY_ADDR, 4, (const uint8_t *)&key);
+    } else if (state == MBOOT_STATE_FSLOAD_END) {
         // The FS-load update completed (either with success or failure), so erase the
         // update key and write the result of the FS-load operation into flash.
         mp_spiflash_erase_block(MBOOT_SPIFLASH_SPIFLASH, SPIFLASH_UPDATE_KEY_ADDR);