[netdrvr 8139cp] PCI MWI cleanup; remove unneeded workaround

[netdrvr 8139cp] PCI MWI cleanup; remove unneeded workaround

* The PCI layer now handles incorrect cacheline size settings,
  as it should.  Remove our own workarounds.
* Move pci_set_mwi up much earlier in the probe process,
  and check its return value.
* Call pci_clear_mwi() in ->probe error handling
* Call pci_clear_mwi() in ->remove