Fix watchdog init code

stm-firmware/safety/watchdog.c

@@ -70,15 +70,24 @@ int watchdog_setup(uint8_t prescaler)
 	/** - Unlock registers */
 	IWDG->KR = STM32_WATCHDOG_REGISTER_ACCESS_KEY;
 
+	/** - Wait until prescaler can be written */
+	while (IWDG->SR & IWDG_SR_PVU);
+
 	/** - Write prescaler value */
 	IWDG->PR = prescaler_reg_val;
 
+	/* - Wait until reload value can be written */
+	while (IWDG->SR & IWDG_SR_RVU);
+
 	/** - Set reload value fixed to 0xFFF */
 	IWDG->RLR = 0xFFFU;
 
 	/** - Write enable key */
 	IWDG->KR = STM32_WATCHDOG_ENABLE_KEY;
 
+	/** - Do a first reset of the counter. This also locks the config regs */
+	watchdog_ack(WATCHDOG_MAGIC_KEY);
+
 	return 0;
 }