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>

board/gdsys/common/cmd_ioloop.c

@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <console.h>
 
 #include <gdsys_fpga.h>