gitlab-ci.d/buildtest: Merge the --without-default-* jobs

gitlab-ci.d/buildtest: Merge the --without-default-* jobs

Let's safe some CI minutes by merging these two jobs. We can now
also drop "--disable-capstone" since the capstone submodule has
been removed a while ago. We should rather test --disable-fdt now
to check a compilation without the "dtc" submodule (for this we
have to drop i386-softmmu from the target list unfortunately).
Additionally, the qtests with s390x and sh4 are not read for
"--without-default-devices" yet, so we can only test mips64 and
avr here now.

Message-Id: <20230130104446.1286773-5-thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>