linux(4): Add a simple rseq syscall implementation.

To avoid annoyng messages from glibc-2.35 test suite add the simple
implementation of rseq syscall which is do nothing for now.

I plan to implement it if and when the API stabilizes.

MFC after: 2 weeks

(cherry picked from commit ee55d560e89ac8de37def993a13d2582638273b7)