smb3: create smb3 equivalent alias for cifs pseudo-xattrs

We really, really don't want to be encouraging people to use
cifs (the dialect) since it is insecure, so to avoid confusion
we want to move them to names which include 'smb3' instead of
'cifs' - so this simply creates an alias for the pseudo-xattrs

e.g. can now do:
getfattr -n user.smb3.creationtime /mnt1/file
and
getfattr -n user.smb3.dosattrib /mnt1/file
and
getfattr -n system.smb3_acl /mnt1/file

instead of forcing you to use the string 'cifs' in
these (e.g. getfattr -n system.cifs_acl /mnt1/file)

Signed-off-by: Steve French <stfrench@microsoft.com>