sh: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
diff --git a/board/renesas/rsk7264/Makefile b/board/renesas/rsk7264/Makefile
index 476de43..7ada697 100644
--- a/board/renesas/rsk7264/Makefile
+++ b/board/renesas/rsk7264/Makefile
@@ -3,23 +3,5 @@
 #
 # SPDX-License-Identifier:	GPL-2.0+
 
-include $(TOPDIR)/config.mk
-
-LIB	= lib$(BOARD).o
-
-OBJS	:= rsk7264.o
-SOBJS	:= lowlevel_init.o
-
-LIB	:= $(addprefix $(obj),$(LIB))
-OBJS	:= $(addprefix $(obj),$(OBJS))
-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	:= rsk7264.o
+obj-y	+= lowlevel_init.o