[RISCV] Move DebugLoc Copy into CompressInstEmitter

Summary:
This copy ensures that debug location information is kept for
compressed instructions. There are places where both compressInstruction and
uncompressInstruction are called that were not doing this copy, discarding some
debug info.

This change merely moves the copy into the generated file, so you cannot forget
to copy the location over when compressing or uncompressing.

Reviewers: asb, luismarques

Reviewed By: luismarques

Subscribers: sameer.abuasal, aprantl, hiraditya, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, kito-cheng, shiva0217, jrtc27, MaskRay, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, Jim, s.egerton, pzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67493