We now have an invariant that all TCG_TYPE_I32 values are
zero-extended, which means that we do not need to extend
them again during qemu_ld/st, either explicitly via a separate
tcg_out_ext32u or implicitly via P_ADDR32.
Reviewed-by: NEmilio G. Cota <cota@braap.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>