sddm-kcm: don't hardcode session file location.
Summary:
The sddm-kcm uses /usr/share/xsessions and /usr/share/wayland-sessions pathes, but in FreeBSD the correct path is /usr/local/share/*.
This cause, that in sddm page of systemsettings, in the part of automatic login, the sessions are empty.
See: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=232356
Reviewers: FreeBSD, Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D16339