We don't need to append the dtb to the kernel image in all cases, with
e.g. the u-boot bootloader we can load the dtb seperately from the
kernel image. Introduce a new variable deviceinfo_append_dtb, if set to
"true", append the dtb, otherwise just copy the dtb file to the boot
partition.
Fixes#260
[ci:ignore-count]
Since a recent kernel update enables the LCD display, this
uses a dts that allows the lcd to function, but drops support
for usb host (since purism does not have an all-in-one dts
yet)
[skip ci]: already built successfully in CI
USB host mode is useful (essential?) on the devkit for adding a
keyboard/mouse to interact with the desktop since the onboard display
and touchscreen are very much in flux.
[skip ci]: already built successfully in CI
