kvm/ppc/booke64: Fix lazy ee handling in kvmppc_handle_exit()

EE is hard-disabled on entry to kvmppc_handle_exit(), so call
hard_irq_disable() so that PACA_IRQ_HARD_DIS is set, and soft_enabled
is unset.

Without this, we get warnings such as arch/powerpc/kernel/time.c:300,
and sometimes host kernel hangs.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>