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/esd/common/cmd_loadpci.c b/board/esd/common/cmd_loadpci.c
index 95d1891..9541817 100644
--- a/board/esd/common/cmd_loadpci.c
+++ b/board/esd/common/cmd_loadpci.c
@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <console.h>
 #if !defined(CONFIG_440)
 #include <asm/4xx_pci.h>
 #endif