thunderbolt: Bond lanes only when dual_link_port != NULL in alloc_dev_default()

We should not dereference ->dual_link_port if it is NULL and lane bonding
is requested. For this reason move lane bonding configuration happen
inside the block where ->dual_link_port != NULL.

Fixes: 54509f50 ("thunderbolt: Add KUnit tests for path walking")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Yehezkel Bernat <YehezkelShB@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Change-Id: I59dc9fc947098bc6b993f97184cdab0460702419