math: fix two fma issues (only affects non-nearest rounding mode, x86)

[musl] / src / fenv / fesetexceptflag.c

#include <fenv.h>

int fesetexceptflag(const fexcept_t *fp, int mask)
{
        feclearexcept(~*fp & mask);
        feraiseexcept(*fp & mask);
        return 0;
}