greybus: Documentation/sysfs: update the example sysfs tree

Update the example sysfs-tree layout under Documentation.

The new layout reflects changes to the kernel device-model that are
needed to eventually be able to handle multiple AP-bridges.

The example tree has two AP-bridges, each with its own view of the
UniPro network, the bus.

.
├── greybus1
│   ├── 1-2
│   │   ├── 1-2.1
│   │   │   ├── class
│   │   │   ├── id
│   │   │   └── state
│   │   ├── 1-2.2
│   │   │   ├── class
│   │   │   ├── id
│   │   │   └── state
│   │   ├── id
│   │   ├── product_id
│   │   ├── unique_id
│   │   └── vendor_id
│   ├── 1-4
│   │   ├── 1-4.2
│   │   │   ├── class
│   │   │   ├── gpbridge0
│   │   │   │   ├── gpio
│   │   │   │   │   └── gpiochip490
│   │   │   │   └── i2c-4
│   │   │   ├── id
│   │   │   └── state
│   │   ├── id
│   │   ├── product_id
│   │   ├── unique_id
│   │   └── vendor_id
│   └── 1-svc
│       ├── ap_intf_id
│       ├── eject
│       ├── endo_id
│       └── unique_id
└── greybus2
    ├── 2-3
    │   ├── 2-3.1
    │   │   ├── class
    │   │   ├── id
    │   │   └── state
    │   ├── id
    │   ├── product_id
    │   ├── unique_id
    │   └── vendor_id
    └── 2-svc
        ├── ap_intf_id
        ├── eject
        ├── endo_id
        └── unique_id

Every bus has exactly one svc device (1-svc and 2-svc). For our system,
the svc device of each bus will be a representation of the same
network-unique SVC device (e.g. endo_id and unique_id will be
identical).

The first bus has two registered interfaces (1-2 and 1-4), while the
second bus has a single interface (2-3). Note that the interface ids (2,
4, and 3) are necessarily unique as these are interfaces on the same
network.

Interface 1-2 has two bundles (1-2.1 and 1-2.2) and interface 1-4 has
a single bundle (1-4.2). The bundle ids are interface-unique and reflect
the ids found in each manifest.

In the example, bundle 1-4.2 has a gbbridge-device, which is the parent
device for a gpiochip device and an i2c bus.

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