hw/intc/grlib_irqmp: implements the multiprocessor status register

hw/intc/grlib_irqmp: implements the multiprocessor status register

This implements the multiprocessor status register in grlib-irqmp and
bind it to a start signal, which will be later wired in leon3-generic
to start a cpu.

The EIRQ and BA bits are not implemented.

Based on https://gaisler.com/doc/gr712rc-usermanual.pdf, §8.3.5.

Co-developed-by: Frederic Konrad <konrad.frederic@yahoo.fr>
Signed-off-by: Clément Chigot <chigot@adacore.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240131085047.18458-4-chigot@adacore.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>