linux(4): Export the AT_RANDOM depending on the process osreldata

AT_RANDOM has appeared in the 2.6.30 Linux kernel first time.

Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D39646
MFC after: 1 month

(cherry picked from commit 40c36c4674eb9602709cf9d0483a4f34ad9753f6)