Fix build failing in do_image_ubimg task

do_image_ubimg was allowed to run before do_deploy_append_mender-uboot
was executed, leading to it not finding uboot.env in the deployment
area. This fixes the problem by forcing the deploy to happen before
do_package, which the image targets will naturally depend on.

Changelog: Title

Signed-off-by: Jonas Norling <jonas.norling@greeneggs.se>
(cherry picked from commit 99d5485)

meta-mender-core/recipes-bsp/u-boot/u-boot-mender.inc

@@ -52,4 +52,4 @@ do_deploy_append_mender-uboot() {
     dd if=/dev/zero of=${WORKDIR}/uboot.env bs=${MENDER_BOOTENV_TOTAL_ALIGNED_SIZE} count=1
     install -m 644 ${WORKDIR}/uboot.env ${DEPLOYDIR}/uboot.env
 }
-addtask deploy after do_compile
+addtask deploy after do_compile before do_package