media: mtk-mdp: convert mtk_mdp_dev.comp array to list

The functions mtk_mdp_register/unregister_component have been created to
add / remove items from the list of components.

This will eventually enable us to specify a list of components in the
device tree instead of hardcoding them into this driver.

The list is modified by a single thread at driver probe time, and will
not be traversed by another thread until the call to pm_runtime_enable
at the end of probing.

Signed-off-by: Eizan Miyamoto <eizan@chromium.org>
Reviewed-by: Enric Balletbo I Serra <enric.balletbo@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>