dahdi: Use ioctl(DAHDI_SPECIFY) instead of legacy /dev/dahdi/%u
dahdi: Use ioctl(DAHDI_SPECIFY) instead of legacy /dev/dahdi/%u

It appears that opening "/dev/dahdi/channel" and using
ioctl(DAHDI_SPECIFY) is possible at least since dahdi 2.4 (from 2010),
and opening "/dev/dahdi/%u" has been deprecated ever since.  One
advantage of the new interface is that you can use channel numbers
larger than 250, which is quite easily possible if you have more than
eight E1 lines on a system.  It also makes libosmo-abis work on systems
where there are no udev rules for creating the legacy device nodes.

Change-Id: Id6c8f27d7ae948b50e9cf5a38f039d782ff78e1d

osmocom/libosmo-abis,osmocom/libosmo-abis,osmocom/libosmo-abis