readline: install configuration file from package recipe

/etc/inputrc is configuration file for readline. However, until now, it
was provided by skeleton. This patch install /etc/inputrc from readline
recipe.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>