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/drivers/fpga/virtex2.c b/drivers/fpga/virtex2.c
index 0d2d9a4..f7cf02a 100644
--- a/drivers/fpga/virtex2.c
+++ b/drivers/fpga/virtex2.c
@@ -12,6 +12,7 @@
  */
 
 #include <common.h>
+#include <console.h>
 #include <virtex2.h>
 
 #if 0