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/video/sunxi/sunxi_display.c b/drivers/video/sunxi/sunxi_display.c
index 46436b8..c45b3eb 100644
--- a/drivers/video/sunxi/sunxi_display.c
+++ b/drivers/video/sunxi/sunxi_display.c
@@ -8,6 +8,7 @@
 
 #include <common.h>
 #include <efi_loader.h>
+#include <time.h>
 
 #include <asm/arch/clock.h>
 #include <asm/arch/display.h>