Added --path switch to match a specific device by USB device path

[dboresjo]

When multiple cards are connected that don't provide real serial numbers (eg BITFT), the --path switch can be used to match a specific device by USB device path instead.

For example, given the following devices connected:

$ uhidctl
Status for relay BITFT at [0001:0040:00], 2 ports:
  Port 1: 0 OFF
  Port 2: 0 OFF
Status for relay BITFT at [0001:006c:00], 2 ports:
  Port 1: 0 OFF
  Port 2: 0 OFF

You can control the device at 0001:0040:00 using:

$ uhidctl -a 1 -p 1 --path 0001:0040:00
Status for relay BITFT at [0001:0040:00], 2 ports:
  Port 1: 1 ON

[mvp]

I have just added new option to change relay serial number fbfb8786344.
I think this should be better solution to this problem?
Please try if it fixes this for your relays.

[dboresjo]

I have just added new option to change relay serial number fbfb8786344. I think this should be better solution to this problem? Please try if it fixes this for your relays.

This is better in theory, however does not help in our case. We have multiple relays deployed and need to operate them remotely.

[mvp]

What stops you from renaming your relays remotely? I just tried it on my 2 test relays, I didn't have any problem renaming them