[clang] [BPF] make __BPF_FEATURE_MAY_GOTO available for cpuv1 (PR #108071)

[via cfe-commits]

4ast wrote:

> @yonghong-song, @4ast,
> 
> As a cleanup, Yonghong suggested moving `__BPF_FEATURE_MAY_GOTO` macro so that it is available for CPUv1. (Although, I think it's better to move both `__BPF_FEATURE_MAY_GOTO` and `__BPF_FEATURE_ADDR_SPACE_CAST` down to CPUv4, as this would be more consistent with kernel features support).
> 
> Wdyt?

why force users to specify -mcpu=v4 ?
may_goto and addr_cast are fine with v1.

https://github.com/llvm/llvm-project/pull/108071