[llvm] [SLP] Partially revert #224931 for alternate nodes (PR #228659)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> The scalar context carries more than its user., for example AMDGPU reads the afn flag of an fdiv and X86 reads the strictfp attribute through it and only the fmul price depends on the user.
> 
> I would drop the context for the fmul alone and keep it for the other opcodes, the way #228902 does for a vector fmul whose lanes get extracted.

To me, all this stuff looks like target-specific, it should be handled in AMDGPU TTI, not in SLP, unless there is a wrong info is passed from SLP. The way how the context should be treated - target decision, not SLP (target-independent) decision

https://github.com/llvm/llvm-project/pull/228659