u-boot.inc: Fix devtool build u-boot for u-boot without menuconfig
For u-boot recipes without menuconfig support, running devtool results
in a do_configure error:
cp: cannot stat '/home/r60874/upstream/fsl-xwayland/tmp/work/imx8mmevk-fsl-linux/u-boot-imx/2018.03-r0/u-boot-imx-2018.03//.config': No such file or directory
The problem arises because u-boot.inc supports recipes with and without
menuconfig.
Fix the problem by properly setting DEVTOOL_DISABLE_MENUCONFIG so that devtool
can control logic that applies only for menuconfig support.
Signed-off-by: Tom Hochstein <tom.hochstein@nxp.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
