[llvm] AMDGPU/GlobalISel: Import D16 load patterns and add combines for them (PR #153178)

[Petar Avramovic via llvm-commits]

petar-avramovic wrote:

> LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-expensive-checks-ubuntu` running on `as-builder-4` while building `llvm` at step 7 "test-check-all".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/187/builds/11235
> Here is the relevant piece of the build log for the reference

https://github.com/llvm/llvm-project/pull/158039

https://github.com/llvm/llvm-project/pull/153178