[Bug target/121970] struct copy still use zmm even specify -mmove-max=256

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121970

--- Comment #6 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---

> > 
> > So this seems like a target issue.
> 
> Ah, I see, thanks.
> 
> H.J, I think we should remove ix86_store_max from MOVE_MAX.

It failed pieces-memset-46.c since 

m_align is decided by MOVE_MAX_PIECES for memset, hmm.