[X86] Prefer rotate by 1 over rotate by imm

Summary:
Rotate by 1 is translated to 1 micro-op, while rotate with imm8 is translated to 2 micro-ops.

Fixes pr30644.

Reviewers: delena, igorb, craig.topper, spatel, RKSimon

Differential Revision: https://reviews.llvm.org/D25399

llvm-svn: 283758