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>
diff --git a/common/cli_hush.c b/common/cli_hush.c
index 296542f..a7cac4f 100644
--- a/common/cli_hush.c
+++ b/common/cli_hush.c
@@ -79,6 +79,7 @@
 #include <malloc.h>         /* malloc, free, realloc*/
 #include <linux/ctype.h>    /* isalpha, isdigit */
 #include <common.h>        /* readline */
+#include <console.h>
 #include <bootretry.h>
 #include <cli.h>
 #include <cli_hush.h>