irqbalance: fix socket directory and create it

irqbalance: fix socket directory and create it

Irqbalance defines /run/irqbalance dir for its socket
communication between irqbalance and its UI. /run does not exist
in OpenWrt (although it is defined by the Linux FHS), so the
socket creation fails. Although we do not compile UI and thus
the issue is not critical to us, fix the directory location.

Additionally, the creation is originally handled by a systemd
init script that we do not use.

* patch source to define dir as /var/run/irqbalance
* create the dir in the procd init script.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>