[X86] Refactor peepholes for masked shift amount into a multiclass

The peephole (shift x, (and y, 31)) -> (shift x, y) is repeated for each
integer type and each shift variant.

To improve this a new multiclass is added that covers all integer types.  The
shift patterns are now instantiated from this.  I am planning to add new
instances for rotates as well.

No functional change intended:

  * test/CodeGen/X86/shift-and.ll provides coverage

  * Compared the expanded tablegen output and matched up the defs for these
    Pat<>s before and after

llvm-svn: 203685