Hello everyone! I am trying to submit a small PR for HStatus register, just to get an idea on how the maintainers feel about bringing in hs and vs extensions into the rust-embedded crate.

I had a small question about which macro to use for implementation, when is

```rs
#[cfg(not(target_arch = "riscv32"))]
read_write_csr_field! {
    Hstatus,
    /// controls the effective XLEN for VS-mode
    /// VSXLEN = 32 when HSXLEN = 32
    /// encoded == to misa.MXL
    vsxl: [32:33],
}

```

Field used, vs enum? My guess is when it can encode multiple values.

```rs
csr_field_enum! {
    /// Endianness mode
    VSBE {
        default: LittleEndian,
        /// Little Endian
        LittleEndian = 0,
        /// Big Endian
        BigEndian = 1,
    }
}

```

But i had seen a single bit flag used for enums i believe in another register implementation