[NFC] Move getAll{S,V}GPR{32,128} methods to SIFrameLowering

Summary:
Future patch needs some of these in multiple places.

The definitions of these can't be in the header and be eligible for
inlining without making the full declaration of GCNSubtarget visible.
I'm not sure what the right trade-off is, but I opted to not bloat
SIRegisterInfo.h

Reviewers: arsenm, cdevadas

Reviewed By: arsenm

Subscribers: RamNalamothu, qcolombet, jvesely, wdng, nhaehnle, hiraditya, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79878