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>

examples/standalone/smc911x_eeprom.c

@@ -15,6 +15,7 @@
  */
 
 #include <common.h>
+#include <console.h>
 #include <exports.h>
 #include <linux/ctype.h>
 #include "../drivers/net/smc911x.h"