usb: improve error message to indicate root cause
usb: improve error message to indicate root cause

When another (Ctlra based, or otherwise) application already
has access to a controller, it is not available for "claiming"
in the USB code. Improve the error message to indicate that
the root cause is probably that another application is already
using the device.

Signed-off-by: Harry van Haaren <6e1296516ee88185cd60d9725251227ece1af74d@gmail.com>

openAVproductions/openAV-Ctlra