change(pycardium): Scale calls to epic_sleep based on systick interval

pycardium/mphalport.c

@@ -246,9 +246,18 @@ static void systick_delay(uint32_t us)
 		while (final_time - systick_get_us() > SYSTICK_INTERVAL_US) {
 			uint32_t sleep_time =
 				(final_time - systick_get_us()) / 1000;
-			if (sleep_time > 100)
-				sleep_time = 100;
+
+			/* We need to wake up at least in SYSTICK_INTERVAL_US to make
+			 * sure we serve the systick interrupt.
+			 * Add some error margin to avoid issues with the clock accuracy
+			 * of epicardium */
+			if (sleep_time > SYSTICK_INTERVAL_US / 1000 / 2) {
+				sleep_time = SYSTICK_INTERVAL_US / 1000 / 2;
+			}
 			epic_sleep(sleep_time);
+			/* epic_sleep() can return early if there was an interrupt
+			 * coming from epicardium side.
+			 * Give MP a chance to handle them. */
 			mp_handle_pending(true);
 		}