post: add blackfin to the post_time_ms list

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/post/post.c b/post/post.c
index d62f10a..8705b12 100644
--- a/post/post.c
+++ b/post/post.c
@@ -495,7 +495,8 @@
  */
 unsigned long post_time_ms(unsigned long base)
 {
-#if defined(CONFIG_PPC) || defined(CONFIG_ARM) && !defined(CONFIG_KIRKWOOD)
+#if defined(CONFIG_PPC) || defined(CONFIG_BLACKFIN) || \
+    (defined(CONFIG_ARM) && !defined(CONFIG_KIRKWOOD))
 	return (unsigned long)lldiv(get_ticks(), get_tbclk() / CONFIG_SYS_HZ)
 		- base;
 #else