drm/modes: Fill drm_cmdline mode from named modes

The current code to deal with named modes will only set the mode name, and
then it's up to drivers to try to match that name to whatever mode or
configuration they see fit.

The plan is to remove that need and move the named mode handling out of
drivers and into the core, and only rely on modes and properties. Let's
start by properly filling drm_cmdline_mode from a named mode.

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-v9-11-24b168e5bcd5@cerno.tech


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