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/cmd_otp.c b/common/cmd_otp.c
index 593bb8c..10c1475 100644
--- a/common/cmd_otp.c
+++ b/common/cmd_otp.c
@@ -16,6 +16,7 @@
 #include <config.h>
 #include <common.h>
 #include <command.h>
+#include <console.h>
 
 #include <asm/blackfin.h>
 #include <asm/clock.h>