graphics/epsonscan2-non-free-plugin: Unbreak build

Fixes build taking into account the Linux version

Co-authored-by: rhurlin@FreeBSD.org

PR: 279825
Approved by: J.R. Oldroyd <fbsd@opal.com> (maintainer)
MFH: 2024Q3

(cherry picked from commit a2ba2e8a3ba655ffac931d7789a2037e53c7c5d8)