[X86][Sched] Update scheduling information for VZEROALL on HWS, BDW, SKX, SNB.

    Summary:
    While looking at PR35606, I found out that the scheduling info is incorrect.

    One can check that it's really a P5+P6 and not a 2*P56 with:
    echo -e 'vzeroall\nvandps %xmm1, %xmm2, %xmm3' | ./bin/llvm-exegesis -mode=uops -snippets-file=-
    (vandps executes on P5 only)

    Reviewers: craig.topper, RKSimon

    Subscribers: llvm-commits

    Differential Revision: https://reviews.llvm.org/D52541

llvm-svn: 343447