target/riscv/kvm: add RVV and Vector CSR regs

target/riscv/kvm: add RVV and Vector CSR regs

Add support for RVV and Vector CSR KVM regs vstart, vl and vtype.

Support for vregs[] requires KVM side changes and an extra reg (vlenb)
and will be added later.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231218204321.75757-5-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>