[SCSI] Switch fdomain to the pci_get API

Doesn't make the hardware hot pluggable but does ensure the driver won't
crash when another device is hot-unplugged at the wrong moment. Soon I
propose to deprecate pci_find_device() and some of its friends.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>