ksmbd: Add kernel-doc for ksmbd_extract_sharename() function

The ksmbd_extract_sharename() function lacked a complete kernel-doc
comment. This patch adds parameter descriptions and detailed function
behavior to improve code readability and maintainability.
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/server/misc.c

@@ -261,6 +261,7 @@ char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name)
 
 /**
  * ksmbd_extract_sharename() - get share name from tree connect request
+ * @um: pointer to a unicode_map structure for character encoding handling
  * @treename:	buffer containing tree name and share name
  *
  * Return:      share name on success, otherwise error