[Bug target/66822] Turn off X86_TUNE_ZERO_EXTEND_WITH_AND for -miamcu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66822
--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> ---
Please hold a bit with this change, I have a patch that improves generation of
zero_extend substantially.