MAINTAINERS: Update email address for Benoit Cousson

Goodbye TI. Welcome new life!

Signed-off-by: Benoit Cousson <bcousson@baylibre.com>
Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
[tony@atomide.com: updated subject for the name]
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Olof Johansson <olof@lixom.net>