Bluetooth: CAP: Fix log warning for meta pointer

Fixes the following warning:
<wrn> cbprintf_package: cbprintf_package_convert:
  (unsigned) char * used for %p argument. It's recommended
  to cast it to void * because it may cause misbehavior in
  certain configurations. String:"%s: meta %p len %zu" argument:1

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>