Revert r313343 "[X86] PR32755 : Improvement in CodeGen instruction selection for LEAs."

This caused PR34629: asserts firing when building Chromium. It also broke some
buildbots building test-suite as reported on the commit thread.

> Summary:
>    1/  Operand folding during complex pattern matching for LEAs has been
>        extended, such that it promotes Scale to accommodate similar operand
>        appearing in the DAG.
>        e.g.
>           T1 = A + B
>           T2 = T1 + 10
>           T3 = T2 + A
>        For above DAG rooted at T3, X86AddressMode will no look like
>           Base = B , Index = A , Scale = 2 , Disp = 10
>
>    2/  During OptimizeLEAPass down the pipeline factorization is now performed over LEAs
>        so that if there is an opportunity then complex LEAs (having 3 operands)
>        could be factored out.
>        e.g.
>           leal 1(%rax,%rcx,1), %rdx
>           leal 1(%rax,%rcx,2), %rcx
>        will be factored as following
>           leal 1(%rax,%rcx,1), %rdx
>           leal (%rdx,%rcx)   , %edx
>
>    3/ Aggressive operand folding for AM based selection for LEAs is sensitive to loops,
>       thus avoiding creation of any complex LEAs within a loop.
>
> Reviewers: lsaba, RKSimon, craig.topper, qcolombet
>
> Reviewed By: lsaba
>
> Subscribers: spatel, igorb, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D35014

llvm-svn: 313376