thunderbolt: Do not clear USB4 router protocol adapter IFC and ISE bits

These fields are marked as vendor defined in the USB4 spec and should
not be modified by the software, so only clear them when we are dealing
with pre-USB4 hardware.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Yehezkel Bernat <YehezkelShB@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>