ksmbd: add default data stream name in FILE_STREAM_INFORMATION

Windows client expect to get default stream name(::DATA) in
FILE_STREAM_INFORMATION response even if there is no stream data in file.
This patch fix update failure when writing ppt or doc files.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Reviewed-By: Tom Talpey <tom@talpey.com>
Signed-off-by: Steve French <stfrench@microsoft.com>