drm/modes: Switch to named mode descriptors

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.tech


Signed-off-by: Maxime Ripard <maxime@cerno.tech>