[llvm] [PowerPC] option `-msoft-float` should not block the PC-relative address instruction (PR #92543)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 commented:

Thanks for improving this.
- In the description, `Fixes #62372` should be a right form to connect this pr and the issue.
- We may also need to check all the places where `hasPrefixInstrs()` is called. Now `hasPrefixInstrs()` does not necessary mean vector instructions are also enabled, so we need to add check for `hasP10Vector()` too. For example for the usages in
  - `llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp`
  - `llvm/lib/Target/PowerPC/PPCISelLowering.cpp`

https://github.com/llvm/llvm-project/pull/92543