linux(4): implement PR_SET_NO_NEW_PRIVS

This makes prctl(2) support PR_SET_NO_NEW_PRIVS, by mapping it
to the native PROC_NO_NEW_PRIVS_CTL procctl(2).

Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30973

(cherry picked from commit 2f514e6f13de41aa9ad5f563ed0decc66e91f99c)