[glibc] powerpc: Update acosf ulps

[Florian Weimer]

* Adhemerval Zanella Netto:

> Because gcc complains due how math_opt_barrier is implemented:
>
> ../sysdeps/ieee754/flt-32/e_acosf.c: In function ‘__ieee754_acosf’:
> ../sysdeps/aarch64/fpu/math-barriers.h:23:30: error: read-only variable ‘__x’ used as ‘asm’ output
>    23 |   ({ __typeof (x) __x = (x); __asm ("" : "+w" (__x)); __x; })
>       |                              ^~~~~
> ../sysdeps/ieee754/flt-32/e_acosf.c:94:16: note: in expansion of macro ‘math_opt_barrier’
>    94 |         return math_opt_barrier (pi2);
>       |                ^~~~~~~~~~~~~~~~

We can fix this by using __typeof (+x).  It removes the const qualifier,
as far as I can see.  If we choose this path, please make the change in
a separate commit.

Thanks,
Florian