[MIPS] pb1000: Replace obsolete memsetup.S with lowlevel_init.S

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
diff --git a/board/pb1x00/Makefile b/board/pb1x00/Makefile
index f7d5841..afe02c2 100644
--- a/board/pb1x00/Makefile
+++ b/board/pb1x00/Makefile
@@ -26,7 +26,7 @@
 LIB	= $(obj)lib$(BOARD).a
 
 COBJS	= $(BOARD).o flash.o
-SOBJS	= memsetup.o
+SOBJS	= lowlevel_init.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))