Cherry-picking Fix csr pipe write handshaking

[zibaiwan]

Fix csr pipe write handshaking

1. If blocking, read valid reg, wait until valid is 0.
2. If non-blocking, read valid reg once ->return failure if valid is 1.
3. write to the pipe.
4. write 1 to the valid.

cherry picked from commit 78dd35424198849280e7a9c9cecab38bdca80f4a