filesystems/zxfer: make property objsetid readonly
Approved by: allanjude (upstream)
Approved by: ports@scaleengine.com (maintainer timeout)
Reported by: dougs@dawnsign.com
PR: 253418
MFH: 2025Q1
(cherry picked from commit 31efecb9ca20446d19333f8582cc75d623c1fe6c)