[CORE] vmm_vcpu_irq: Fix vmm_vcpu_irq_deassert() semantics

The patch "[CORE] vmm_vcpu_irq.c: refactor a bit the code" changed
vmm_vcpu_irq_deassert() and forece vcpu irq deassert request to be
ordered after vcpu irq assert request. In other words, we can only
deassert vcpu irq if it was asserted previously else dessert request
is ignored.

In case of ARM32VE (or any architecture that supports vcpu irq assert
and vcpu irq deassert), it is not mandatory that vcpu irq deassert
will always follow vcpu irq assert. The ordering of vcpu irq assert
and vcpu irq deassert is architecture dependent. In case of ARM32VE,
the generic timer code induces a vcpu irq deassert before vcpu irq
assert via GIC emulator to route HW virtual timer irq to VCPU.

This patch again makes vcpu irq assert and vcpu irq deassert
unordered.

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