media: MAINTAINERS: rectify entry for MEDIATEK MEDIA DRIVER

Commit 9cdd70ce ("media: dt-bindings: media: mtk-vcodec: Separate video
encoder and decoder dt-bindings") converts and splits mediatek-vcodec.txt
to mediatek,vcodec-{de,en}coder.yaml, but missed to adjust its reference
in MAINTAINERS.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains about a
broken reference.

Repair this file reference in MEDIATEK MEDIA DRIVER.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>