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/power/battery/bat_trats.c b/drivers/power/battery/bat_trats.c
index bfde692..089e789 100644
--- a/drivers/power/battery/bat_trats.c
+++ b/drivers/power/battery/bat_trats.c
@@ -6,6 +6,7 @@
  */
 
 #include <common.h>
+#include <console.h>
 #include <power/pmic.h>
 #include <power/battery.h>
 #include <power/max8997_pmic.h>