media: MAINTAINERS: Add entry for Techwell TW9910

Add entry for Techwell TW9910 video decoder. The driver is currently
orphaned.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>