fru: Fix I2CDevice `Bus` type

Summary:
Added debug logs and saw that the bus associated with the EntityManager
path was always 0. Manually checking with `busctl` showed the correct
value.
```
root@platform30:~# pcie_bifurcation
Parsing host 0
Start Getting Via Entity Manager for /xyz/openbmc_project/inventory/system/board/HPM0
Path: /xyz/openbmc_project/inventory/system/board/ssd_hpm0
Bus: 0
Updating 0 with /xyz/openbmc_project/inventory/system/board/ssd_hpm0

root@platform30:~# busctl introspect xyz.openbmc_project.EntityManager \
> /xyz/openbmc_project/inventory/system/board/ssd_hpm0 | grep \\.Bus
.Bus                                              property  t         4
```

Turns out the `Bus` size for I2CDevice of Entity Manager(uint64) is
different than that of FruDevice `Bus` size(uint32)
https://www.alteeve.com/w/List_of_DBus_data_types#:~:text=0%20to%2018%2C446%2C744%2C073%2C709%2C551%2C616.-,DBus%3A%20t,-Perl%3A%20uint64

```
root@platform30:~# busctl introspect xyz.openbmc_project.EntityManager /xyz/openbmc_project/inventory/system/board/HPM0
xyz.openbmc_project.Inventory.Decorator.I2CDevice    interface -         -                                        -
.Address                                             property  t         80                                       emits-change
.Bus                                                 property  t         28                                       emits-change

root@platform30:~# busctl introspect xyz.openbmc_project.FruDevice /xyz/openbmc_project/FruDevice/platform30
xyz.openbmc_project.FruDevice       interface -         -                                    -
.ADDRESS                            property  u         80                                   emits-change
.BUS                                property  u         28                                   emits-change
```

Update the data type accordingly.

Tested:
The Entity Manager path is now successfully related to the correct
bus.
```
Start Getting Via Entity Manager for /xyz/openbmc_project/inventory/system/board/HPM0
Path: /xyz/openbmc_project/inventory/system/board/ssd_hpm0
Bus: 4
Updating 4 with /xyz/openbmc_project/inventory/system/board/ssd_hpm0
Finished parsing host 0
Parsing host 1
Start Getting Via Entity Manager for /xyz/openbmc_project/inventory/system/board/HPM1
Finished parsing host 1
Got bus 4, addr 83, bifurcation
Using Server3PcieBifurcation implementation
Failed to get deviceLanes: sd_bus_message_read_basic fundamental: System.Error.ENXIO: No such device or address
Failed to get slotLanes: sd_bus_call: org.freedesktop.DBus.Error.UnknownProperty: Unknown interface xyz.openbmc_project.Inventory.Item.PCIeDevice or property Lanes.
```

Google-Bug-Id: 435526024
Change-Id: I147ce675ee527902c8389f4e179724c10fc5ebc2
Signed-off-by: Kyle Nieman <kyle.nieman@fii-na.corp-partner.google.com>