We should have 'n', then 'size', not the opposite.
This is harmless because the 2 values are just multiplied, but having
the correct order silence a (unpublished yet) smatch warning.

While at it use '*tun_seg' instead '*seg'. The both variable have the same
type, so the result is the same, but it lokks more logical.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>