common: main.c: make show_boot_progress __weak

This not only looks a bit better it also prevents a
warning with W=1 (no previous prototype).

Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
Acked-by: Simon Glass <sjg@chromium.org>

common/main.c

@@ -17,8 +17,7 @@ DECLARE_GLOBAL_DATA_PTR;
 /*
  * Board-specific Platform code can reimplement show_boot_progress () if needed
  */
-void inline __show_boot_progress (int val) {}
-void show_boot_progress (int val) __attribute__((weak, alias("__show_boot_progress")));
+__weak void show_boot_progress(int val) {}
 
 static void modem_init(void)
 {