usb: ehci-pci: Set PROBE_PREFER_ASYNCHRONOUS

This driver often takes on the order of 8ms to start, but every little
bit counts. It shouldn't have many cross-device dependencies to
race with, nor racy access to shared state with other drivers, so this
should be a relatively low risk change.

This driver was pinpointed as part of a survey of top slowest initcalls
(i.e., are built in, and probing synchronously) on a lab of ChromeOS
systems.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20221028184507.v2.1.I9a5353f81d1509f85f3a04f0cdc9099f6fe60811@changeid


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>