MAINTAINERS: change 842 NX owner email address

Change my IBM email to my personal IEEE email.

I'm leaving IBM, so my email there won't work anymore.  This changes
the owner to my personal email, so I can still get cc'ed on patches,
until someone at IBM sends a patch to take it over.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>