lasips2: introduce port IRQ and new lasips2_port_init() function

lasips2: introduce port IRQ and new lasips2_port_init() function

Introduce a new lasips2_port_init() QOM init function for the LASIPS2_PORT type
and use it to initialise a new gpio for use as a port IRQ. Add a new qemu_irq
representing the gpio as a new irq field within LASIPS2Port.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Helge Deller <deller@gmx.de>
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220712215251.7944-25-mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>