thunderbolt: Correct path indices for PCIe tunnel

PCIe tunnel path indices got mixed up when we added support for tunnels
between switches that are not adjacent. This did not affect the
functionality as it is just an index but fix it now nevertheless to make
the code easier to understand.

Reported-by: Rajmohan Mani <rajmohan.mani@intel.com>
Fixes: 8c7acaaf ("thunderbolt: Extend tunnel creation to more than 2 adjacent switches")
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Yehezkel Bernat <YehezkelShB@gmail.com>