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/misc/tegra186_bpmp.c b/drivers/misc/tegra186_bpmp.c
index b3ed03e..89e27dd 100644
--- a/drivers/misc/tegra186_bpmp.c
+++ b/drivers/misc/tegra186_bpmp.c
@@ -5,6 +5,7 @@
 
 #include <common.h>
 #include <dm.h>
+#include <time.h>
 #include <dm/lists.h>
 #include <dm/root.h>
 #include <mailbox.h>