powerpc/64s: Use the HV handler for external IRQ replay in HV mode on POWER9

POWER9 host external interrupts use the h_virt_irq_common handler, so
use that to replay them rather than using the hardware_interrupt_common
handler. Both call do_IRQ, but using the correct handler reduces
i-cache footprint.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>