Zvk: Implement Zvksed, vector SM4 Block Cipher

Implement the Zvksed sub-extension, "ShangMi Suite: SM4 Block Cipher":
 - vsm4k.vi, vector SM4 key expansion,
 - vsm4r.{vs,vv}, vector SM4 rounds.

This also introduces a header for common vector SM4 logic.

Co-authored-by: Raghav Gupta <rgupta@rivosinc.com>
Co-authored-by: Albert Jakieła <aja@semihalf.com>
Signed-off-by: Eric Gouriou <ego@rivosinc.com>