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

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66822

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Yulia Koval from comment #1)
> I think it's a good idea.

If we do that, we may also adjust iamcu_cost:

  COSTS_N_INSNS (3),                    /* cost of movsx */
  COSTS_N_INSNS (2),                    /* cost of movzx */