thunderbolt: Allow USB3 bandwidth to be lower than maximum supported

Currently USB3 tunnel setup fails if USB4 link available bandwidth is too low
to allow USB3 Maximum Supported Link Rate. In reality, this limitation is not
needed, and may cause failure of USB3 tunnel establishment, if USB4 link
available bandwidth is lower than USB3 Maximum Supported Link Rate. E.g. if we
connect to USB4 v1 host router, a USB4 v1 device router, via 10 Gb/s cable.
Hence, here we discard this limitation, and now we only limit USB3 bandwidth
allocation to be not higher than 90% of USB3 Max Supported Link Rate (for first
USB3 tunnel only).

Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>