[rtl872x] Fixes D7 configuration when exiting hibernate mode

[XuGuohui]

Problem

D7 (PA27) outputs high after entering hibernate mode, even if it is configured as OUTPUT and outputs LOW before sleep.

Solution

Configure the PA27 to be no-pull ability before entering hibernate mode.

Steps to Test

Run the attached application.

Example App

void setup() {
    pinMode(D7, OUTPUT);
    digitalWrite(D7, LOW);

    delay(2s);
    System.sleep(SystemSleepConfiguration().mode(SystemSleepMode::HIBERNATE).duration(5s));
}

References

N/A

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)