Use a common e-mail for myself at Kaffeine

I'm deprecating my mchehab@s-opensource.com email. While this
is there on just one place, let's update my e-mail along a
few other places.

While here, as we don't receive an patches from the Kaffeine
maintainer for versions 1.x since we migrated to KF5 and
launched version 2.x (about 2 years ago), let's also update
the maintainership status to reflect it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>