kselftest: devices: Add sample board file for google,spherion

kselftest: devices: Add sample board file for google,spherion

Add a sample board file describing the file's format and with the list
of devices expected to be probed on the google,spherion machine as an
example.

Test output:

TAP version 13
Using board file: boards/google,spherion.yaml
1..8
ok 1 /usb2-controller@11200000/1.4.1/camera.device
ok 2 /usb2-controller@11200000/1.4.1/camera.0.driver
ok 3 /usb2-controller@11200000/1.4.1/camera.1.driver
ok 4 /usb2-controller@11200000/1.4.2/bluetooth.device
ok 5 /usb2-controller@11200000/1.4.2/bluetooth.0.driver
ok 6 /usb2-controller@11200000/1.4.2/bluetooth.1.driver
ok 7 /pci-controller@11230000/0.0/0.0/wifi.device
ok 8 /pci-controller@11230000/0.0/0.0/wifi.driver
Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: "Nícolas F. R. A. Prado" <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20240122-discoverable-devs-ksft-v4-2-d602e1df4aa2@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>