net: thunderbolt: Fix typos in comments

Fix two typos in comments:

  blongs -> belongs
  UPD -> UDP

No functional changes.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>