linux-dtb.inc: drop unused DTB_NAME variable from do_install
* this is causing do_install to depend on KERNEL_IMAGE_BASE_NAME which
in some cases contains something like BUILD_NUMBER from CI, that
caused do_install to be reexecuted every single time, which is very
sad to be caused by unused variable.
* jethro and newer don't need this change, because it's also fixed in
commit
86b3f29f93e3f87903668ea317c6bd97be4cdf62
Author: Marek Vasut <marex@denx.de>
Date: Thu May 14 14:31:11 2015 +0200
Subject: kernel: Build DTBs early
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
