[CORE] vmm_vcpu_irq: Protect arch_vcpu_irq_xxx() using vcpu irqs spinlock

For SMP Guest running on SMP host, we don't want multiple host CPUs to
execute arch_vcpu_irq_xxx() simultaneously for given VCPU hence, we use
vcpu irqs spinlock to protect calls to arch_vcpu_irq_xxx().

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