target/riscv: rvk: add support for zbkc extension

target/riscv: rvk: add support for zbkc extension

 - reuse partial instructions of zbc extension, update extension check for them

Signed-off-by: Weiwei Li <[email protected]>
Signed-off-by: Junqiang Wang <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-Id: <20220423023510[email protected]>
Signed-off-by: Alistair Francis <[email protected]>