avsbus-control: Add system-specific scripts

The avsbus-control scripts differ between different machine
configurations. Rename the existing ones to witherspoon-* and
add the swift-* ones. Install the appropriate script depending
on the machine being built.

Tested: Built swift and witherspoon and verified that the scripts
        rootfs/usr/bin/ were the ones for the machine being built.

Change-Id: If6a223f2972680769d526c0ef53cf5ca82337721
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
7 files changed