Please be aware that starting with AIX 7.2, the CIFS/SMBFS client feature will no longer be supported.
The CIFS filesets (bos.cifs_fs.*) can still be found on the AIX 7.2 Expansion Pack -- previously bos.cifs_fs was on the base AIX OS image.
More information can be found in the AIX 7.2 announcement letter at the link below:
17 June 2018