KVM: PPC: Book3E HV: call RECONCILE_IRQ_STATE to sync the software state

Rather than calling hard_irq_disable() when we're back in C code
we can just call RECONCILE_IRQ_STATE to soft disable IRQs while
we're already in hard disabled state.

This should be functionally equivalent to the code before, but
cleaner and faster.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
[agraf: fix comment, commit message]
Signed-off-by: Alexander Graf <agraf@suse.de>