[SVE] Remove calls to getBitWidth from PowerPC

Reviewers: efriedma, sdesmalen, hfinkel, david-arm, fpetrogalli

Reviewed By: efriedma, fpetrogalli

Subscribers: wuzish, nemanjai, tschuett, hiraditya, kbarton, rkruppe, psnobl, shchenz, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77900