cros_bundle_firmware: Remove deprecated uboot+dtb property
cros_bundle_firmware: Remove deprecated uboot+dtb property

This is no longer used so it is safe to remove it.

BUG=chrome-os-partner:13961
BRANCH=none
TEST=manual
In U-Boot source:
$ grep uboot+dtb `find . -name *dts*`

See that there is nothing.

Also build and boot on link.

Change-Id: Ia32d8bb59b5354a54a1de445ce9a6bed1092e38a
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39872
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

coreos/dev-util,marineam/coreos-dev-util,coreos/dev-util,mgireesh05/dev-util,mgireesh05/dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util