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/power/pmic/stpmic1.c b/drivers/power/pmic/stpmic1.c
index de31934..2297af4 100644
--- a/drivers/power/pmic/stpmic1.c
+++ b/drivers/power/pmic/stpmic1.c
@@ -9,6 +9,7 @@
 #include <i2c.h>
 #include <misc.h>
 #include <sysreset.h>
+#include <time.h>
 #include <dm/device.h>
 #include <dm/lists.h>
 #include <power/pmic.h>