[SPARC64]: Update MAINTAINERS entry.

ultralinux@vger is deprecated, folks should use
sparclinux@vger for both sparc ports.

Eddie, Anton, and Jakub haven't been active in
sparc64 maintainence for years, so best to remove
them as reports do nothing more than fill up their
mailboxes :)

Signed-off-by: David S. Miller <davem@davemloft.net>