MAINTAINERS & files: Canonize the e-mails I use at files

From now on, I'll start using my @kernel.org as my development e-mail.

As such, let's remove the entries that point to the old
mchehab@s-opensource.com at MAINTAINERS file.

For the files written with a copyright with mchehab@s-opensource,
let's keep Samsung on their names, using mchehab+samsung@kernel.org,
in order to keep pointing to my employer, with sponsors the work.

For the files written before I join Samsung (on July, 4 2013),
let's just use mchehab@kernel.org.

For bug reports, we can simply point to just kernel.org, as
this will reach my mchehab+samsung inbox anyway.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Brian Warner <brian.warner@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>