Bug when doing analogWrite() then digitalWrite()

Hi,
there is a bug when doing analogWrite() then digitalWrite() on a pwm pin. The pin will kept being configured as a pwm output and the digitalWrite() will have no effect.

In the following snippet, the Built-in LED will kept being controlled by PWM.

```
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
analogWrite(LED_BUILTIN, 20);
digitalWrite(LED_BUILTIN, HIGH);
}

void loop() {}
```

Start by tracing the SAMD21 implementations of analogWrite() and digitalWrite() for PWM-capable pins, using the provided sketch as the reproducer. Check how pin output mode is restored after analogWrite(); done means a subsequent digitalWrite(LED_BUILTIN, HIGH) takes effect instead of leaving the pin under PWM control.

Written by the indexing model from the issue text.