netinet6: Fix my style issues

Reported by: pouria
Reviewed by: pouria, ziaee, glebius
Approved by: glebius
Fixes: 31ec8b6407fdd5a87d70265762457c67ce618283
Differential Revision: https://reviews.freebsd.org/D55136

(cherry picked from commit 4548149a81026ad9b1706b2b7e7ad47a4c1358b6)

Reviewed by: glebius, kp, pouria, zlei
Approved by: glebius, pouria
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D54382