common: Move clock functions into a new file

These three clock functions don't use driver model and should be migrated.
In the meantime, create a new file to hold them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/t104xrdb/diu.c b/board/freescale/t104xrdb/diu.c
index aa56b8e..25c8597 100644
--- a/board/freescale/t104xrdb/diu.c
+++ b/board/freescale/t104xrdb/diu.c
@@ -4,6 +4,7 @@
  * Author: Priyanka Jain <Priyanka.Jain@freescale.com>
  */
 
+#include <clock_legacy.h>
 #include <asm/io.h>
 #include <common.h>
 #include <command.h>
diff --git a/board/freescale/t104xrdb/spl.c b/board/freescale/t104xrdb/spl.c
index a1c8a47..2306d03 100644
--- a/board/freescale/t104xrdb/spl.c
+++ b/board/freescale/t104xrdb/spl.c
@@ -3,6 +3,7 @@
  */
 
 #include <common.h>
+#include <clock_legacy.h>
 #include <console.h>
 #include <env_internal.h>
 #include <init.h>