tcg: Adjust tcg_out_label for const

tcg: Adjust tcg_out_label for const

Simplify the arguments to always use s->code_ptr instead of
take it as an argument.  That makes it easy to ensure that
the value_ptr is always the rx version.

Reviewed-by: Joelle van Dyne <j@getutm.app>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>