PCI: Do not run NVidia quirks related to MSI with MSI disabled
There is no reason to run NVidia-specific quirks related to HT MSI
mappings with MSI disabled via pci=nomsi, so make
__nv_msi_ht_cap_quirk() return immediately in that case.
This allows at least one machine to boot 100% of the time with
pci=nomsi (it still doesn't boot reliably without that).