[CORE] vmm_host_irq: Process multiple active IRQs from vmm_host_irq_exec()

Currently, we only process on interrupt in vmm_host_irq_exec(). This is
not optimal because we might have multiple interrupts pending in irqchip.

This patch renames vmm_host_irq_exec() to vmm_host_active_irq_exec() and
improves it to process all pending interrupts in irqchip.

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