thunderbolt: Reduce retry timeout to speed up boot for some devices

This is a followup to "thunderbolt: Workaround an IOMMU fault on certain
systems with Intel Maple Ridge".

It seems like the timeout can be reduced to 250ms. This reduces the overall
delay caused by the retires to ~1s. This is about the time other things
being initialized in parallel need anyway*, so like this the effective boot
time is no longer compromised.

*I only had a single device available for my measurements: A Clevo X170KM-G
desktop replacement notebook.

Signed-off-by: Werner Sembach <wse@tuxedocomputers.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>