greybus: interface: clean up ES2 VID/PID hack

Clean up the ES2 VID/PID hack using a new quirk flag.

Note that the hack is now used if and only if the interface is a Toshiba
ES2 bridge (and not if the attributes read zero).

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>