sh: Fix building ecovec board

Build error was with board/renesas/ecovec/lowlevel_init.S
include/version.h: Assembler messages:
include/version.h:41: Error: unknown opcode
lowlevel_init.S:48: Error: unknown opcode
lowlevel_init.S:51: Error: unknown opcode
etc

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/board/renesas/ecovec/Makefile b/board/renesas/ecovec/Makefile
index 8fdc0c9..b592a9c 100644
--- a/board/renesas/ecovec/Makefile
+++ b/board/renesas/ecovec/Makefile
@@ -25,8 +25,12 @@
 COBJS   := ecovec.o
 SOBJS   := lowlevel_init.o
 
-$(LIB): $(obj).depend $(COBJS) $(SOBJS)
-		$(call cmd_link_o_target, $(COBJS) $(SOBJS))
+SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS))
+SOBJS	:= $(addprefix $(obj),$(SOBJS))
+
+$(LIB): $(OBJS) $(SOBJS)
+		$(call cmd_link_o_target, $(OBJS) $(SOBJS))
 
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