[usbdev/doc] Add recipe for wake from low power
[usbdev/doc] Add recipe for wake from low power

Provide instructions demonstrating how to enter and exit low power mode
for the suspend/resume cycle.
Instructions assume the use of usbdev_aon_wake and pinmux.

Signed-off-by: Alexander Williams <d0fb8a15e7b6f5e62278a4cf44515038c232186c@google.com>

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