Blackfin: cache core/system clock values

Calculating the clocks requires a bit of calls to gcc math functions, so
cache the values after the first run since they'll most likely never
change once U-Boot is up and running.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/lib_blackfin/Makefile b/lib_blackfin/Makefile
index 93f7d4f..46ef7f3 100644
--- a/lib_blackfin/Makefile
+++ b/lib_blackfin/Makefile
@@ -39,6 +39,7 @@
 COBJS-y	+= board.o
 COBJS-y	+= boot.o
 COBJS-y	+= cache.o
+COBJS-y	+= clocks.o
 COBJS-y	+= muldi3.o
 COBJS-$(CONFIG_POST) += post.o tests.o
 COBJS-y	+= string.o