target-arm: Fix VMLA, VMLS, VNMLS, VNMLA handling of NaNs
Correct handling of NaNs for VFP VMLA, VMLS, VNMLS and VNMLA requires that
we implement the set of negations and additions specified by the ARM ARM;
plausible looking simplifications like turning (-A + B) into (B - A) or
computing (A + B) rather than (B + A) result in selecting the wrong NaN or
returning a NaN with the wrong sign bit.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>