Moved STDIO_UART defines for UBLOX_EVK_ODIN_W2

[andreaslarssonublox]

Description

Moved STDIO_UART defines to targets.json for UBLOX_EVK_ODIN_W2 instead of hardcoded.
The default UART(D2/D8) can be overriden in mbed_app.json like this:

"target_overrides": {
        "UBLOX_EVK_ODIN_W2": {
            "target.stdio_uart_tx": "D1",
            "target.stdio_uart_rx": "D0",
            "target.stdio_uart": "UART_3"
        }
}

Status

Should be reviewed and tested by @andrewc-arm to make sure it solves #5129

Migrations

NO

Related PRs

#5129

Todos

None

Deploy notes

None

Steps to test or reproduce

Have only run one test case to verify that it is still possible to run 'mbed test'.

[andreaslarssonublox]

Forgot the USBTX and USBRX defines. Creating a new PR to have a cleaner git history.