[X86] Clean up test/CodeGen/X86/2006-03-01-InstrSchedBug.ll

Summary:
- Migrated from grep to FileCheck.
- Re-indented, removed boilerplate comments.
- Added 'entry' label at beginning of basic block.

Patch by Jorge Gorbe!

Reviewed By: RKSimon

Subscribers: RKSimon, jgorbe, llvm-commits

Differential Revision: https://reviews.llvm.org/D30317

llvm-svn: 298298