[source] uboot-zynq: fix compile error for be short of dtc

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/e7dc511e640b00f4ec381248c317cb6370bd798e

commit e7dc511e640b00f4ec381248c317cb6370bd798e
Author: Yutang Jiang <yutang.jiang at nxp.com>
AuthorDate: Wed Oct 19 19:20:21 2016 +0800

    uboot-zynq: fix compile error for be short of dtc
    
    While enable zynq uboot:
    CONFIG_PACKAGE_uboot-zynq-zc702
    CONFIG_PACKAGE_uboot-zynq-zed
    CONFIG_PACKAGE_uboot-zynq-zybo
    
    make will arise dtc error:
    ./scripts/dtc-version.sh: line 17: dtc: command not found
    ./scripts/dtc-version.sh: line 18: dtc: command not found
    *** Your dtc is too old, please upgrade to dtc 1.4 or newer
    make[4]: *** [checkdtc] Error 1
    
    Pass the kernel dtc to uboot for compile.
    
    Signed-off-by: Yutang Jiang <yutang.jiang at nxp.com>
---
 package/boot/uboot-zynq/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/package/boot/uboot-zynq/Makefile b/package/boot/uboot-zynq/Makefile
index 412415b..a6e4f0a 100644
--- a/package/boot/uboot-zynq/Makefile
+++ b/package/boot/uboot-zynq/Makefile
@@ -6,6 +6,7 @@
 #
 
 include $(TOPDIR)/rules.mk
+include $(INCLUDE_DIR)/image.mk
 
 PKG_NAME:=u-boot
 PKG_VERSION:=2016.03
@@ -81,7 +82,7 @@ endef
 
 define Build/Compile
 	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) \
-		CROSS_COMPILE=$(TARGET_CROSS)
+		CROSS_COMPILE=$(TARGET_CROSS) DTC=$(LINUX_DIR)/scripts/dtc/dtc
 endef
 
 define Package/uboot/install/default