[CORE] devemu: More flexible guest irq emulation APIs

This patch deprecates old "emupic" based APIs for emulating guest irqs. The old approach did not suit well for emulating GPIO lines and muxed IO lines as dummy interrupt lines.

As per the new guest irq APIs, we don't have any "emupic" in guest. Instead we N guest irq lines per-guest (N specified via guest device tree). The guest irq lines are used as actual irq lines to guest PIC and as dummy irq lines for emulating muxed IO lines.

There also slight improvment seen in __vmm_devemu_emulate_irq() with the new approach for guest irqs.

Signed-off-by: Anup Patel <anup@brainfault.org>