blackfin: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Sonic Zhang <sonic.zhang@analog.com>
diff --git a/board/bf609-ezkit/Makefile b/board/bf609-ezkit/Makefile
index cd2fdc7..3bfd088 100644
--- a/board/bf609-ezkit/Makefile
+++ b/board/bf609-ezkit/Makefile
@@ -9,31 +9,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(BOARD).o
-
-COBJS-y	:= $(BOARD).o
-COBJS-$(CONFIG_BFIN_SOFT_SWITCH)   += soft_switch.o
-
-SRCS	:= $(SOBJS-y:.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) $(SOBJS))
-
-clean:
-	rm -f $(SOBJS) $(OBJS)
-
-distclean:	clean
-	rm -f $(LIB) core *.bak $(obj).depend
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################
+obj-y	:= bf609-ezkit.o
+obj-$(CONFIG_BFIN_SOFT_SWITCH)   += soft_switch.o