[AArch64][SVE] Re-submit patch series for ZIP1/ZIP2

This patch resubmits the SVE ZIP1/ZIP2 patch series consisting of
of r320992, r320986, r320973, and r320970 by reverting
https://reviews.llvm.org/rL321024.

The issue that caused r321024 has been addressed in https://reviews.llvm.org/rL321158,
so this patch-series should be safe to resubmit.

llvm-svn: 321163