stm32/mboot: Add board-configurable SysTick hook.

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

ports/stm32/mboot/main.c

@@ -1518,9 +1518,9 @@ void SysTick_Handler(void) {
     // work properly.
     SysTick->CTRL;
 
-    // Update the LED0 state from here to ensure it's consistent regardless of
+    // Run any board-specific code that needs to be done regardless of
     // other processing going on in interrupts or main.
-    led0_update();
+    MBOOT_BOARD_SYSTICK();
 }
 
 #if defined(MBOOT_I2C_SCL)

ports/stm32/mboot/mboot.h

@@ -54,6 +54,10 @@
 #define MBOOT_BOARD_STATE_CHANGE(state, arg) mboot_state_change_default((state), (arg))
 #endif
 
+#ifndef MBOOT_BOARD_SYSTICK
+#define MBOOT_BOARD_SYSTICK() mboot_ui_systick()
+#endif
+
 #ifndef MBOOT_ADDRESS_SPACE_64BIT
 #define MBOOT_ADDRESS_SPACE_64BIT (0)
 #endif
@@ -148,7 +152,7 @@ extern uint8_t _estack[ELEM_DATA_SIZE];
 
 void systick_init(void);
 void led_init(void);
-void led0_update(void);
+void mboot_ui_systick(void);
 void SystemClock_Config(void);
 
 uint32_t get_le32(const uint8_t *b);

ports/stm32/mboot/ui.c

@@ -122,7 +122,7 @@ void led0_state(led0_state_t state) {
     }
 }
 
-void led0_update(void) {
+void mboot_ui_systick(void) {
     if (led0_cur_state != LED0_STATE_OFF && systick_ms - led0_ms_interval > 50) {
         uint8_t rate = (led0_cur_state >> 2) & 0x1f;
         led0_ms_interval += 50;