I am not familiar with VSC and am not certain if the following is VSC version dependent.
This is from the VSC 4.2.1 admin guide - I hope it helps you modify the controller password:
https://library.netapp.com/ecm/ecm_download_file/ECMP1149724
p42
VSC uses credentials (user name and password) that you set up in Monitoring and Host
Configuration to authenticate each storage system and determine which storage operations can be
performed on that storage system. VSC uses one set of credentials for each storage system. These
credentials determine all VSC tasks that can be performed on that storage system; in other words, the
credentials are for VSC, not an individual VSC user.
p46
When Monitoring and Host Configuration adds a storage system, it displays a pop-up box that lists
the credentials associated with the username/ password pair you entered when you logged in. You
can either set up default credentials that Monitoring and Host Configuration will use during its
storage system discovery process or manually enter credentials when the storage system is
discovered.
Thanks,
Kevin