tcg/optimize: Add one's mask to TempOptInfo

Add o_mask mirroring z_mask, but for 1's instead of 0's.
Drop is_const and val fields, which now logically overlap.

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