target/nios2: Deprecate the Nios II architecture

See commit 9ba1caf5 ("MAINTAINERS: Mark the Nios II CPU as orphan"),
last contribution from Chris was in 2012 [1] and Marek in 2018 [2].

[1] https://lore.kernel.org/qemu-devel/1352607539-10455-2-git-send-email-crwulff@gmail.com/
[2] https://lore.kernel.org/qemu-devel/805fc7b5-03f0-56d4-abfd-ed010d4fa769@denx.de/



Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20231117070250.32932-1-philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231120150833.2552739-6-alex.bennee@linaro.org>