Double check handling of pins used by drivers

[bjoernQ]

This currently compiles while it shouldn't

#[entry]
fn main() -> ! {
    let peripherals = Peripherals::take();
    let system = SystemControl::new(peripherals.SYSTEM);
    let clocks = ClockControl::boot_defaults(system.clock_control).freeze();

    let mut io = Io::new(peripherals.GPIO, peripherals.IO_MUX);
    let pins = TxRxPins::new_tx_rx(
        &mut io.pins.gpio4,
        &mut io.pins.gpio5,
    );

    let mut serial1 = Uart::new_with_config(
        peripherals.UART1,
        Config::default(),
        Some(pins),
        &clocks,
        None,
    );

    io.pins.gpio4.into_push_pull_output(); // this shouldn't compile since the pin is used by the UART driver

    let delay = Delay::new(&clocks);

    println!("Start");
    loop {
        serial1.write_byte(0x42).ok();
        let read = block!(serial1.read_byte());

        match read {
            Ok(read) => println!("Read 0x{:02x}", read),
            Err(err) => println!("Error {:?}", err),
        }

        delay.delay_millis(250);
    }
}

Easiest here probably is to align the API and have it similar to SPI master (i.e. with_tx / with_rx etc.)?

[Dominaezzz]

When using the I2S peripheral in camera mode, most people will need to give the vsync pin to the peripheral but also separately listen for interrupts on the pin.

So I guess this depends on whether the peripheral is reading the pin or writing to it.