super0: use define for char array in examine_super0

super0: use define for char array in examine_super0

Using nb with 11 length may cause format-truncation errors,
because it was possible to use snprintf with 12 length input
and write it to 11 length output. Added new define and use it
to avoid this error.

Signed-off-by: Kinga Stefaniuk <kinga.stefaniuk@intel.com>