[hdctools]: Servod- Support Newer Kernels

Since kernel 3.4, beaglebone has moved from using the sysfs omapmux's
to using device tree for pin muxing.

Therefore only use the pin muxes on the older 3.2 kernel.

I2C now starts counting from 0 rather than 1 so this addresses that as

TEST=Built and successfully ran servod on Kernel 3.8 and ensure Kernel
3.2 images still worked with the changes.

Change-Id: Ib27447484197b2b5e6ddd0d937a984063e8bfa19
Reviewed-on: https://chromium-review.googlesource.com/179743
Tested-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
8 files changed