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_simple.c b/common/cli_simple.c
index d8b40c9..9c3d073 100644
--- a/common/cli_simple.c
+++ b/common/cli_simple.c
@@ -12,6 +12,7 @@
 #include <common.h>
 #include <bootretry.h>
 #include <cli.h>
+#include <console.h>
 #include <linux/ctype.h>
 
 #define DEBUG_PARSER	0	/* set to 1 to debug */