[AMDGPU] Update code object description
- Use ELF header flags to identify processor.
- Remove isa note record.
- Add target feature section.
- Make metadata for NumVGPRs, NumSGPRs and MaxFlatWorkGroupSize required.
- Add FixedWorkGroupSize to CodeProps metadata.
- Add ReqdWorkGroupSize* to kernel descriptor and move MaxFlatWorkGroupSize to be adjacent.
- Move IsXNACKEnabled in the kernel descriptor to be at the end of the unused flags.
- Remove IsDynamicCallStack from the metadata and kernel descriptor.
- Remove legacy debugger metadata.
- Remove old XNACK enabled processor names.
Differential Revision: https://reviews.llvm.org/D39828
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317855
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