[AVX512] Make the itinerary parameter actually pass through the the...

[AVX512] Make the itinerary parameter actually pass through the the AVX512_maskable_common multiclass

Summary: This looks to have been disconnected about 3 years ago in r219358.

Reviewers: gadi.haber, RKSimon, zvi

Reviewed By: gadi.haber

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36658

llvm-svn: 310844