net/subnetcalc: Update 2.7.1 => 2.7.5

Changelog:
https://github.com/dreibh/subnetcalc/blob/subnetcalc-2.7.5/ChangeLog

Commit log:
https://github.com/dreibh/subnetcalc/compare/subnetcalc-2.7.1...subnetcalc-2.7.5

PR: 297195
Reported by: Thomas Dreibholz <thomas.dreibholz@gmail.com> (maintainer)
Approved by: osa, vvd (Mentors, implicit)