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 <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Closes: lore.kernel.org/r/[e-mail]
Cc: Richard Weinberger <[e-mail]>
Cc: [e-mail]
Reviewed-by: Zhihao Cheng <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

fs/ubifs/auth.c

···
 #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