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/board/freescale/mpc8569mds/mpc8569mds.c b/board/freescale/mpc8569mds/mpc8569mds.c
index 836578f..122490c 100644
--- a/board/freescale/mpc8569mds/mpc8569mds.c
+++ b/board/freescale/mpc8569mds/mpc8569mds.c
@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <console.h>
 #include <hwconfig.h>
 #include <pci.h>
 #include <asm/processor.h>