smb3: add module alias for smb3 to cifs.ko

We really don't want to be encouraging people to use the old
(less secure) cifs dialect (SMB1) and it can be confusing for them
with SMB3 (or later) being recommended but the module name is cifs.

Add a module alias for "smb3" to cifs.ko to make this less confusing.

Signed-off-by: Steve French <smfrench@gmail.com>