AMDGPU: Add round-to-odd rounding during f64 to bf16 conversion (#133995)

f64 -> bf16 conversion can be lowered to f64 -> f32 followed by f32 ->
bf16:
   v_cvt_f32_f64_e32 v0, v[0:1]
   v_cvt_pk_bf16_f32 v0, v0, s0
Both conversion instructions will do round-to-even rounding, and thus we
will have double rounding issue which may generate incorrect result in
some data range. We need to add round-to-odd rounding during f64 -> f32
to avoid double rounding,.

NOTE: we are having the same issue with f64 -> f16 conversion. Will add
round-to-odd rounding for it in a separate patch, which fixes
SWDEV-523856

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Co-authored-by: Matt Arsenault <arsenm2@gmail.com>

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