target/riscv: Add property check for Zvfh{min} extensions

target/riscv: Add property check for Zvfh{min} extensions

Add check for Zvfh and Zvfhmin.

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20230215020539.4788-7-liweiwei@iscas.ac.cn>
[Palmer: commit text]
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>