[clang] [HIP] change default offload archs (PR #139281)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

So we will wait until amdgcnspirv uses SPRIV backend by default, then switch HIP default offload arch to amdgcnspirv. That sounds a reasonable solution to me.

https://github.com/llvm/llvm-project/pull/139281