manual: update /dev management section.

This patch updates the /dev management section in the manual with information
about eudev, which replaces udev.

Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>