The current named mode parsing relies only on the mode name, and doesn't
allow to specify any other parameter.

Let's convert that string list to an array of a custom structure that will
hold the name and some additional parameters in the future.
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Link: https://lore.kernel.org/r/20220728-rpi-analog-tv-properties-v9-10-24b168e5bcd5@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>