[AMDGPU] Prefer v_madak_f32 over v_madmk_f32 to reduce vgpr pressure (#72506)

As explained in the comment in SIInstrInfo::FoldImmediate, if we have a
choice between v_madak_f32 and v_madmk_f32 we should choose the former
so that the literal that is not folded into the instruction can be
materialized in an sgpr instead of a vgpr.