installer/hikey/flash-all.sh: update to flash vendor partition

since the vendor partition is enabled with change here:
https://android-review.googlesource.com/c/device/linaro/hikey/+/660832

Test: manually with HiKey

Change-Id: Ie91bdae93e9e486865b1ff26656232f9a0239a9e
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
diff --git a/installer/hikey/flash-all.sh b/installer/hikey/flash-all.sh
index 87465a4..a4170dd 100755
--- a/installer/hikey/flash-all.sh
+++ b/installer/hikey/flash-all.sh
@@ -76,5 +76,6 @@
 fastboot flash nvme "${INSTALLER_DIR}"/nvme.img
 fastboot flash boot "${OUT_IMGDIR}"/boot.img
 fastboot flash system "${OUT_IMGDIR}"/system.img
+fastboot flash vendor "${OUT_IMGDIR}"/vendor.img
 fastboot flash cache "${OUT_IMGDIR}"/cache.img
 fastboot flash userdata "${OUT_IMGDIR}"/userdata.img