hw/sparc: Make grlib-irqmp device handle its own inbound IRQ lines

hw/sparc: Make grlib-irqmp device handle its own inbound IRQ lines

Currently the GRLIB_IRQMP device is used in one place (the leon3 board),
but instead of the device providing inbound gpio lines for the board
to wire up, the board code itself calls qemu_allocate_irqs() with
the handler function being a set_irq function defined in the code
for the device.

Refactor this into the standard setup of a device having input
gpio lines.

This fixes a trivial Coverity memory leak report (the leon3
board code leaks the IRQ array returned from qemu_allocate_irqs()).

Fixes: Coverity CID 1421922
Signed-off-by: Peter Maydell <[email protected]>
Message-Id: <20201212144134[email protected]>
Reviewed-by: KONRAD Frederic <[email protected]>
Signed-off-by: Mark Cave-Ayland <[email protected]>