PCI: Avoid broken MSI on SB600 USB devices

Some ATI SB600 USB adapters advertise MSI, but if INTx is disabled by
setting PCI_COMMAND_INTX_DISABLE, MSI doesn't work either.  The PCI/PCIe
specs do not require software to set PCI_COMMAND_INTX_DISABLE when enabling
MSI, but Linux has done that for many years.

Mick reported that 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI
devices") broke these devices.  Prior to 306c54d0edb6, they used INTx.
Starting with 306c54d0edb6, they use MSI, and and the fact that Linux sets
PCI_COMMAND_INTX_DISABLE means both INTx and MSI are disabled on these
devices.

Avoid this SB600 defect by disabling MSI so we use INTx as before.

Fixes: 306c54d0edb6 ("usb: hcd: Try MSI interrupts on PCI devices")
Link: https://lore.kernel.org/r/[email protected]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215690
Link: https://lore.kernel.org/all/PxIByDyBRcsbpcmVhGSNDFAoUcMmb78ctXCkw6fbpx25TGlCHvA6SJjjFkNr1FfQZMntYPTNyvEnblxzAZ8a6jP9ddLpKeCN6Chi_2FuexU=@protonmail.com/
Link: https://lore.kernel.org/r/[email protected]
BugLink: https://lore.kernel.org/all/[email protected]/
Reported-by: Mick Lorain <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>

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