HTIF does not match pseudo spec and other implementations

[abukharmeh]

In RV32, writes to tohost could be interpreted in more than a single way depending on when HTIF tick happens.

This was reported earlier #69 and was 'fixed' in 848312c.

However, I am not sure that this fix is factually correct, as according to this comment riscv-software-src/riscv-isa-sim#364 (comment) , blocking device character is not be supported in RV32 and only syscalls are supported.

This claim is supported by this snippet in PK https://github.com/riscv-software-src/riscv-pk/blob/2f3e6f530384b4ab9f8b39bceb8e86f2ba51a835/machine/htif.c#L92-L107