[llvm] PPC: Move definitions of predicates with features (PR #157058)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Was there a specific reason you moved these within the section documented as CPU Directives vs moving this to just after that section and right before the section labeled:

It's right after the actual features driving the predicates. The feature sets below are less relevant 

https://github.com/llvm/llvm-project/pull/157058