tcg/optimize: Simplify fold_andc constant checks

If operand 2 is constant, then the computation of z_mask and a_mask
will produce the same results as the explicit check via fold_xi_to_i.
Shift the calls of fold_xx_to_i and fold_ix_to_not down below the
i2->is_const check.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed