docker: Add DOCKER_FROM arg

The dockerfile for each architecture is the same except for the 'FROM' image.
Add a new Dockerfile argument DOCKER_FROM that allows for a commom dockerfile.
If the docker version is older than 17.05 generate a docker file from
the common one.

Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>