[libclc] [libclc] Implement __clc_get_local_size/__clc_get_max_sub_group_size for amdgcn (PR #153785)

[Wenju He via cfe-commits]

wenju-he wrote:

https://github.com/llvm/llvm-project/pull/153785/commits/a8fcf405007d05d123f397f66b4139d53586c1b5 is a minor fix to return 1 for out-of-bound dim

https://github.com/llvm/llvm-project/pull/153785