Add Debian packaging

Somewhat based on what the kernel creates with make deb-pkg but modified to make it more like a proper Debian package.

Later on we want to rename things like

linux-image-5.4.0-1-librem5

(that is swap API version and kernel type) but that's not possible since we have another naming out in the wild for 5.3. That's also the reason why we have to pick a API version of h1 (to be 'greater' than g).

Can be built with:

dpkg-buildpackage -uc -us -B --host-arch=arm64

See also #107 (closed)

Marking as wip so it does not get merge accidentally, it should be mostly good to go so allow for in field kernel updates.

Signed-off-by: Guido Günther guido.gunther@puri.sm