mips: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
diff --git a/board/pb1x00/Makefile b/board/pb1x00/Makefile
index ed7370f..647eb85 100644
--- a/board/pb1x00/Makefile
+++ b/board/pb1x00/Makefile
@@ -5,25 +5,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(BOARD).o
-
-COBJS	= $(BOARD).o flash.o
-SOBJS	= lowlevel_init.o
-
-SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-SOBJS	:= $(addprefix $(obj),$(SOBJS))
-
-$(LIB):	$(obj).depend $(OBJS) $(SOBJS)
-	$(call cmd_link_o_target, $(OBJS) $(SOBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################
+obj-y	= pb1x00.o flash.o
+obj-y	+= lowlevel_init.o