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/arch/m68k/cpu/mcf52x2/speed.c b/arch/m68k/cpu/mcf52x2/speed.c
index 0f274ad..02ef5d8 100644
--- a/arch/m68k/cpu/mcf52x2/speed.c
+++ b/arch/m68k/cpu/mcf52x2/speed.c
@@ -8,6 +8,7 @@
  */
 
 #include <common.h>
+#include <clock_legacy.h>
 #include <asm/processor.h>
 #include <asm/immap.h>
 #include <asm/io.h>
@@ -15,7 +16,7 @@
 DECLARE_GLOBAL_DATA_PTR;
 
 /* get_clocks() fills in gd->cpu_clock and gd->bus_clk */
-int get_clocks (void)
+int get_clocks(void)
 {
 #if defined(CONFIG_M5208)
 	pll_t *pll = (pll_t *) MMAP_PLL;