manibuilder: Prepare for official multi-arch images

Now that we can use official multi-arch images prepare for tag names
matching the upstream ones. These will be prefixed with their respective
architecture, e.g. `ppc64le/`. To make the existing dockerfiles for
Debian and Ubuntu usable with the official images, remove their
`-debootstrap` suffix.

Change-Id: I11a7d13c7eb976205093f16dc9d3f5a57bc8f1bb
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73433
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
4 files changed