linuxkpi: Add user_write_access_*
Needed by drm-kmod v5.8
Reviewed by: bz
MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D34284
(cherry picked from commit 4f689b302fc49fc11d19169386f6ccfad05f47dd)