Remove the deprecated moxie target

There are no known users of this CPU anymore, and there are no
binaries available online which could be used for regression tests,
so the code has likely completely bit-rotten already. It's been
marked as deprecated since two releases now and nobody spoke up
that there is still a need to keep it, thus let's remove it now.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210430160355.698194-1-thuth@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
[Commit message typos fixed, trivial conflicts resolved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>