[X86][Haswell]: Updating the scheduling information for the Haswell subtarget.

[X86][Haswell]: Updating the scheduling information for the Haswell subtarget.

Updated the scheduling information for the Haswell subtarget with the following changes:

Regrouped the instructions after adding appropriate load + store latencies.
Added scheduling for missing instructions such as the GATHER instrs.
The changes were made after revisiting the latencies impact of all memory uOps.

Reviewers: RKSimon, zvi, craig.topper, apilipenko
Differential Revision: https://reviews.llvm.org/D40021

Change-Id: Iaf6c1f5169add1552845a8a566af4e5a359217a7
llvm-svn: 320137