common: Move get_ticks() function out of common.h

This function belongs in time.h so move it over and add a comment.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/sound/broadwell_i2s.c b/drivers/sound/broadwell_i2s.c
index 998792b..3d57740 100644
--- a/drivers/sound/broadwell_i2s.c
+++ b/drivers/sound/broadwell_i2s.c
@@ -12,6 +12,7 @@
 #include <common.h>
 #include <dm.h>
 #include <i2s.h>
+#include <time.h>
 #include <asm/io.h>
 #include "broadwell_i2s.h"