hw/pci-host/gpex: Allow more than 4 legacy IRQs

hw/pci-host/gpex: Allow more than 4 legacy IRQs

Some boards such as vmapple don't do real legacy PCI IRQ swizzling.
Instead, they just keep allocating more board IRQ lines for each new
legacy IRQ. Let's support that mode by giving instantiators a new
"nr_irqs" property they can use to support more than 4 legacy IRQ lines.
In this mode, GPEX will export more IRQ lines, one for each device.

Signed-off-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20241223221645.29911-9-phil@philjordan.eu>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>