args: fix documentation to reflect the correct numbers

The macro uses up to 15 arguments.  Reflect this in the top level comment.

Link: https://lkml.kernel.org/r/20251201201018.765475-1-andriy.shevchenko@linux.intel.com
Fixes: d51e783c17ba ("lsm: count the LSMs enabled at compile time")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>