Rewrite doc/keventd.md from a 14-line stub into comprehensive
documentation covering all features of the new unified keventd:
device node creation, persistent symlinks, firmware loading,
module loading, coldplug, conditions, and command-line usage.
Update doc/conditions.md to list keventd as the primary provider
of dev/* and sys/pwr/* conditions, with devmon as fallback when
an external device manager is used instead.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Joachim Wiberg