xpp: Replace drv_attrs with drv_groups on kernels > 3.12

drv_attrs was fully removed from the bus structure in upstream commit
e18945b159a1cdbc031f1d3b0b7e515a33bdcbf7 which was merged into 3.13.

This is necessary to compile against linux kernel version 3.13.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Acked-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
build_tools/dkms-helper: Helper script for DKMS integration.

DKMS (Dynamic Kernel Module Support) [1] provides a mechanism where kernel
modules can be automatically updated when a new kernel is booted.  This is a
simple helper script to automate the process of adding dahdi-linux to the local
DKMS system.

[1] http://linux.dell.com/dkms/

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Acked-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
wcte13xp: Fix bug preventing recover timing from ever being set

A bug introduced in v2.8.0 prevented the recover timing configuration from
being set properly on the hardware. This caused the card to never go into
recovered timing mode.

Signed-off-by: Russ Meyerriecks <rmeyerriecks@digium.com>
Signed-off-by: Shaun Ruffell <sruffell@digium.com>