[SCSI] ipr: Tolerate not finding PCI-X registers

Don't fail initialization of an adapter if the PCI-X registers
cannot be found since it may be a PCI-E adapter.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>