tcg: Introduce tcgv_{i32,i64,ptr}_{arg,temp}

tcg: Introduce tcgv_{i32,i64,ptr}_{arg,temp}

Transform TCGv_* to an "argument" or a temporary.
For now, an argument is simply the temporary index.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>