codal_port/microbit_display: Stop animations when calling clear().

Following the semantics of micro:bit v1.

Fixes issue #150.

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

Author: dpgeorge

src/codal_port/drv_display.c

@@ -142,6 +142,8 @@ void microbit_display_update(void) {
 }
 
 void microbit_display_clear(void) {
+    // Reset repeat state, cancel animation and clear screen.
+    // The actual screen clearing will be done by microbit_display_update.
     wakeup_event = false;
     async_mode = ASYNC_MODE_CLEAR;
     async_tick = async_delay - MILLISECONDS_PER_MACRO_TICK;

src/codal_port/microbit_display.c

@@ -163,7 +163,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(microbit_display_read_light_level_obj, microbit_displa
 
 mp_obj_t microbit_display_clear_func(mp_obj_t self) {
     (void)self;
-    microbit_hal_display_clear();
+    microbit_display_clear();
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_1(microbit_display_clear_obj, microbit_display_clear_func);