The Nios II target is deprecated since v8.2 in commit 9997771b
("target/nios2: Deprecate the Nios II architecture").

Remove:
- Buildsys / CI infra
- User emulation
- System emulation (10m50-ghrd & nios2-generic-nommu machines)
- Tests

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Marek Vasut <marex@denx.de>
Message-Id: <20240327144806.11319-3-philmd@linaro.org>