sh: Fix SH-boards compile error

By Cleanup out-or-tree building for some boards (.depend)
(commit:c8a3b109f07f02342d097b30908965f7261d9f15)
because filse ware changed, some SH-boards have compile error.
I revised this problem.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/board/r7780mp/Makefile b/board/r7780mp/Makefile
index 0ab6d1d..c100e7e 100644
--- a/board/r7780mp/Makefile
+++ b/board/r7780mp/Makefile
@@ -22,7 +22,7 @@
 
 LIB	= $(obj)lib$(BOARD).a
 
-OBJS	:= r7780mp.o
+COBJS	:= r7780mp.o
 SOBJS	:= lowlevel_init.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)