[X86][mingw] Modify the alignment of __m128/__m256/__m512 vector type for mingw

This is a follow up patch after D78564 and D108887.

Martin helped to confirm the alignment in GCC mingw is the same as the
size of vector. https://reviews.llvm.org/D108887#inline-1040893

Reviewed By: mstorsjo

Differential Revision: https://reviews.llvm.org/D109265