[X86] Lower AVX512 and SSE intrinsics for CVTTPD2DQ to X86ISD::CVTTPD2DQ.

Summary: This allows the SSE intrinsic to use the EVEX instruction when available. It also fixes EVEX to not use a weird (v4i32 (fp_to_sint v2f64)) node and it merges some isel patterns. This also fixes some cases that weren't combining vzmovl with cvttpd2dq to remove extra moves.

Reviewers: delena, zvi, RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26330

llvm-svn: 286344