Merge remote-tracking branch 'remotes/rth-gitlab/tags/pull-fpu-20210603' into staging

Finish conversion of float128 and floatx80 to FloatParts.
Implement float128_muladd and float128_{min,max}*.
Optimize int-to-float conversion with hard-float.

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* remotes/rth-gitlab/tags/pull-fpu-20210603: (29 commits)
  softfloat: Use hard-float for {u}int64_to_float{32,64}
  tests/fp: Enable more tests
  softfloat: Convert modrem operations to FloatParts
  softfloat: Move floatN_log2 to softfloat-parts.c.inc
  softfloat: Convert float32_exp2 to FloatParts
  softfloat: Convert floatx80 compare to FloatParts
  softfloat: Convert floatx80_scalbn to FloatParts
  softfloat: Convert floatx80 to integer to FloatParts
  softfloat: Convert floatx80 float conversions to FloatParts
  softfloat: Convert integer to floatx80 to FloatParts
  softfloat: Convert floatx80_round_to_int to FloatParts
  softfloat: Convert floatx80_round to FloatParts
  softfloat: Convert floatx80_sqrt to FloatParts
  softfloat: Convert floatx80_div to FloatParts
  softfloat: Convert floatx80_mul to FloatParts
  softfloat: Convert floatx80_add/sub to FloatParts
  tests/fp/fp-test: Reverse order of floatx80 precision tests
  softfloat: Adjust parts_uncanon_normal for floatx80
  softfloat: Introduce Floatx80RoundPrec
  softfloat: Reduce FloatFmt
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>