[Bug libgcc/116017] libgcc/riscv/softfp: Fix loss of sign when truncating NaN values

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116017

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Can you test also:
```

        #include <stdio.h>
        #include <math.h>

        int main(void)
        {
            volatile double    d;
            volatile float f;

            d = (double) NAN;
            d = -d;
            f = d;
            printf("%a\n", d);
            // Note there is an implicit conversion to double here ...
            printf("%a\n", f);
            volatile double    d1;
            d1 = f;
            printf("%a\n", d1);
            return signbit(d) != signbit(ld);
        }
```