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/nvme/nvme.c b/drivers/nvme/nvme.c
index f915817..cddcc2f 100644
--- a/drivers/nvme/nvme.c
+++ b/drivers/nvme/nvme.c
@@ -9,6 +9,7 @@
 #include <errno.h>
 #include <memalign.h>
 #include <pci.h>
+#include <time.h>
 #include <dm/device-internal.h>
 #include "nvme.h"