setup_usb_configfs: Make it possible to choose the used UDC

[dos1]

Some devices may have more than one UDC available.

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I did it while working on the Librem 5 port, but it turned out to be unnecessary with correctly configured kernel ;) Posting it anyway since it may be useful for other devices in the future and generally seems like a reasonable thing to do.

[gschwind]

Hello,

Maybe my shell knowledge is wrong, but I don't see any difference to make:

echo "$(ls somepath)"

or

UDC="$(ls somepath)"
echo "$UDC"

The explanation look misleading.

[dos1]

@gschwind The important part is if [ -z "$UDC" ]; then.

[gschwind]

Ok if I infer correctly you want to be able change the info.sh to include the choice of UDC

But currently there is no configuration that doing this.