Move console definitions into a new console.h file

The console includes a global variable and several functions that are only
used by a small subset of U-Boot files. Before adding more functions, move
the definitions into their own header file.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/main.c

@@ -10,6 +10,7 @@
 #include <common.h>
 #include <autoboot.h>
 #include <cli.h>
+#include <console.h>
 #include <version.h>
 
 DECLARE_GLOBAL_DATA_PTR;