serial: jsm: change maintainer to myself

Since Thadeu left IBM, jsm has gone mostly unmaintained, since his email
address doesn't work anymore.  I'm stepping up to help maintain this
driver upstream.

I'm adding Thadeu's personal e-mail address in Cc, hoping that we can
get his ack.

Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Cc: Thadeu Cascardo <cascardo@cascardo.eti.br>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>