ksmbd: replace struct dentry with struct path in some function's arguments

For user namespace support, we need to pass
struct user_namespace with struct dentry
to some functions. For reducing the number
of arguments, replace the struct dentry with
struct path in these functions.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>