[X86][LWP] Add llvm support for LWP instructions (reapplied).

Description

[X86][LWP] Add llvm support for LWP instructions (reapplied).

This patch adds support for the the LightWeight Profiling (LWP) instructions which are available on all AMD Bulldozer class CPUs (bdver1 to bdver4).

Reapplied - this time without changing line endings of existing files.

Differential Revision: https://reviews.llvm.org/D32769