RFR: 8370579: PPC: fix inswri immediate argument order

[Manuel Hässig]

This cleanup PR swaps and renames the immediate arguments of the two `insrwi` instruction macros in `ppc.ad` such that they correspond to the order and names in the manual. This involved swapping the arguments in all six usages. I hope this saves the next person trying to reason about this some confused hours.

Testing:
 - [ ] Github Actions
 - [ ] Running some relevant tests (`compiler/c2/TestCharShortByteSwap.java`, `jdk/java/lang/Short/BitTwiddle.java`, `jdk/java/lang/Integer/BitTwiddle.java`, `compiler/codegen/Test6431242.java`) in qemu

-------------

Commit messages:
 - ppc.ad: swap arguments of insrwi

Changes: https://git.openjdk.org/jdk/pull/27978/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27978&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370579
  Stats: 13 lines in 1 file changed: 0 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/27978.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27978/head:pull/27978

PR: https://git.openjdk.org/jdk/pull/27978