board: ti: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Tom Rini <trini@ti.com>
diff --git a/board/ti/am3517crane/Makefile b/board/ti/am3517crane/Makefile
index d9ab72a..9da795d 100644
--- a/board/ti/am3517crane/Makefile
+++ b/board/ti/am3517crane/Makefile
@@ -8,21 +8,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(BOARD).o
-
-COBJS	:= am3517crane.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	:= am3517crane.o