Merge pull request adafruit#9141 from dhalbert/serial_bytes_available

Runtime.serial_bytes_available: return count instead of bool

Author: tannewt

main.c

@@ -50,9 +50,9 @@
 #include "supervisor/cpu.h"
 #include "supervisor/filesystem.h"
 #include "supervisor/port.h"
-#include "supervisor/serial.h"
 #include "supervisor/shared/reload.h"
 #include "supervisor/shared/safe_mode.h"
+#include "supervisor/shared/serial.h"
 #include "supervisor/shared/stack.h"
 #include "supervisor/shared/status_leds.h"
 #include "supervisor/shared/tick.h"