PCI: portdrv: enable device before irq initialization

Call pci_enable_device() before initializing service irqs, because
legacy interrupt is initialized in pci_enable_device() on some
architectures.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>