nand-spl: Use scripts/Makefile.build

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/nand_spl/board/freescale/p1023rds/Makefile b/nand_spl/board/freescale/p1023rds/Makefile
index dbdfa19..652590d 100644
--- a/nand_spl/board/freescale/p1023rds/Makefile
+++ b/nand_spl/board/freescale/p1023rds/Makefile
@@ -3,10 +3,8 @@
 #
 # SPDX-License-Identifier:	GPL-2.0+
 #
-NAND_SPL := y
-PAD_TO := 0xfff01000
 
-include $(TOPDIR)/config.mk
+PAD_TO := 0xfff01000
 
 nandobj	:= $(OBJTREE)/nand_spl/
 
@@ -104,10 +102,3 @@
 
 $(obj)%.o:	$(obj)%.c
 	$(CC) $(CFLAGS) -c -o $@ $<
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################