Fixing compilation errors

[lcckey]

Hi, thanks for your repo and work on this keyboard!
This fix allowed me to build Vial for the Corne v4.1 mini by removing the protocol from the json, fixing #13 / #7
I've also fixed the errors which come up about RGB_MATRIX_SLEEP

[Jufralice]

No no, I think that this should not be merged. I did the exact same two changes a few months ago.
The RGB_MATRIX_SLEEP fix is indeed needed.
But you should not remove the "protocol": "serial_usart" from rev4_1/info.json
This fixed the compilation error but then when you flash your keyboard the two halves are not communicating with each other anymore.
If you don't have the same problem. It might be because you have a mini and I have a 'not-mini'? But I suspect that other peoples might get the same problem as me if they remove that 'serial_usart'

To fix the problem, I had to add back the protocol: "serial_usart" in rev4_1/info.json and to get rid of the compilation error I changed this:

                     "properties": {
                         "protocol": {
                             "type": "string",
-                            "enum": ["custom", "i2c", "serial"]
+                            "enum": ["custom", "i2c", "serial", "serial_usart"]
                         },

in /data/schemas/keyboard.jsonschema
(this removal was done here: qmk/qmk_firmware#23668 by someone who stated that 'serial_usart' was not needed anymore but apparently it was still needed at least for me...)

Or maybe that instead of removing the protocol: "serial_usart" of rev4_1/info.json we should actually replace it by 'serial' .
But I can't test that anymore since I apparently have a new issue preventing my two part to talk to each other anymore.
Something similar to foostan/crkbd#282 apparently...