ubifs: auth.c: fix kernel-doc function prototype warning

Use the correct function name in the kernel-doc comment to prevent
a kernel-doc warning:

auth.c:30: warning: expecting prototype for ubifs_node_calc_hash(). Prototype was for __ubifs_node_calc_hash() instead
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: lore.kernel.org/r/202311052125.gE1Rylox-lkp@intel.com
Cc: Richard Weinberger <richard@nod.at>
Cc: linux-mtd@lists.infradead.org
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/auth.c

@@ -18,7 +18,7 @@
 #include "ubifs.h"
 
 /**
- * ubifs_node_calc_hash - calculate the hash of a UBIFS node
+ * __ubifs_node_calc_hash - calculate the hash of a UBIFS node
  * @c: UBIFS file-system description object
  * @node: the node to calculate a hash for
  * @hash: the returned hash