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/clk/clk_stm32mp1.c b/drivers/clk/clk_stm32mp1.c
index e223f84..3718970 100644
--- a/drivers/clk/clk_stm32mp1.c
+++ b/drivers/clk/clk_stm32mp1.c
@@ -10,6 +10,7 @@
 #include <regmap.h>
 #include <spl.h>
 #include <syscon.h>
+#include <time.h>
 #include <vsprintf.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>