Issue: Device nodes in sysroot image may be broken down

The device nodes are created during packing sysroot in fakeroot
environment. However, the device nodes will become normal files after
packing if the created 'device files' in build/<machine>/sysroot/dev
directory are read-only.

To make sure the device nodes always available in sysroot image.
We force to remove the dev directory and recreate an empty one
before packing sysroot.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Add demo OS installer to customize console configurations

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Add polling loop to get ONIE boot device

ONIE boot device may be not ready immediately after kernel booting.
The polling loop will check if the ONIE boot device is ready or not
every 0.1 sec. It is a total of 7 seconds in the worst case.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Accton AS5712_54X: Add to support ONIE

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Accton AS5712_54X: Add to init USB hub device

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>