board: arm: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Prafulla Wadaskar <prafulla@marvell.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Vipin Kumar <vipin.kumar@st.com>
Cc: Tom Warren <twarren@nvidia.com>
Cc: Tom Rini <trini@ti.com>
diff --git a/board/teejet/mt_ventoux/Makefile b/board/teejet/mt_ventoux/Makefile
index 641e61e..66f56fd 100644
--- a/board/teejet/mt_ventoux/Makefile
+++ b/board/teejet/mt_ventoux/Makefile
@@ -6,21 +6,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(BOARD).o
-
-COBJS	:= $(BOARD).o
-
-SRCS	:= $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-
-$(LIB):	$(obj).depend $(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
+obj-y	:= mt_ventoux.o