[X86] X86FixupVectorConstants - create f32/f64 broadcast constants if the...

[X86] X86FixupVectorConstants - create f32/f64 broadcast constants if the source constant data was f32/f64

This partially reverts 33819f3b - the asm comments become a lot messier in #73509 - we're better off ensuring the constant data is the correct type in DAG