AMDGPU: Add pass to detect used kernel features

AMDGPU: Add pass to detect used kernel features

Mark kernels that use certain features that require user
SGPRs to support with kernel attributes. We need to know
before instruction selection begins because it impacts
the kernel calling convention lowering.

For now this only detects the workitem intrinsics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252323 91177308-0d34-0410-b5e6-96231b3b80d8