board: powerpc: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Kim Phillips <kim.phillips@freescale.com>
Cc: York Sun <yorksun@freescale.com>
Cc: Stefan Roese <sr@denx.de>
diff --git a/board/freescale/mpc8540ads/Makefile b/board/freescale/mpc8540ads/Makefile
index 08dd14b..6f82c7f 100644
--- a/board/freescale/mpc8540ads/Makefile
+++ b/board/freescale/mpc8540ads/Makefile
@@ -5,27 +5,7 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(BOARD).o
-
-COBJS-y	+= $(BOARD).o
-COBJS-y	+= ddr.o
-COBJS-y	+= law.o
-COBJS-y	+= tlb.o
-
-SRCS	:= $(SOBJS:.o=.S) $(COBJS-y:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS-y))
-SOBJS	:= $(addprefix $(obj),$(SOBJS-y))
-
-$(LIB):	$(obj).depend $(OBJS) $(SOBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################
+obj-y	+= mpc8540ads.o
+obj-y	+= ddr.o
+obj-y	+= law.o
+obj-y	+= tlb.o