[MachineCopyPropagation] Remove logic to recognise and delete no-op moves produced after forwarded uses (#167336)

As reported in <https://github.com/llvm/llvm-project/issues/166870>,
some copies with src==reg are not no-ops, e.g. when self-assigning a
w-reg on AArch64 which will zero-extend the corresponding x register.

Revert in order to fix the issue. We may revisit whether the
optimisation can be made safe at a later point.

Reverts dffbc030e75b758e7512518abd499a0f680addbf.
Fixes #166870.

0 files changed, 0 insertions, 0 deletions