[SCSI] ipr: Get rid of superfluous call to pci_disbale_msi/msix()

There is no need to call pci_disable_msi() or pci_disable_msix()
in case the call to pci_enable_msi() or pci_enable_msix() failed.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>