hw/intc/loongson_ipi: Rename LoongsonIPI -> LoongsonIPIState

hw/intc/loongson_ipi: Rename LoongsonIPI -> LoongsonIPIState

We'll have to add LoongsonIPIClass in few commits,
so rename LoongsonIPI as LoongsonIPIState for clarity.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
[PMD: Extracted from bigger commit, added commit description]
Co-Developed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Tested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <20240805180622.21001-2-philmd@linaro.org>