common: Move main_loop() to init.h

Move this function out of common.h and into a better place.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>

common/board_r.c

@@ -26,6 +26,7 @@
 #include <env_internal.h>
 #include <fdtdec.h>
 #include <ide.h>
+#include <init.h>
 #include <initcall.h>
 #if defined(CONFIG_CMD_KGDB)
 #include <kgdb.h>