TF700T: add support for ec_wakeup (device)

* Added DockEmbeddedController class for access EC data
* Added support for toggle ec_wakeup (asusdec)
* Added AutoParts dock preference (ec_wakeup)

Change-Id: I11c5e298de3a31612a0f339415d2a7bf3adbaaa4
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>