[rtl872x] fix millis() may jump after ~37 hours.

[XuGuohui]

Problem

If left running, the P2 millis count will suddenly skip ~3200 seconds between the 36 - 37 hour mark.

Solution

Handle the sys timer overflow in correct manner.

Steps to Test

Run the attached app.

Example App

#include "Particle.h"

SYSTEM_MODE(AUTOMATIC);
SYSTEM_THREAD(ENABLED);

SerialLogHandler logHandler(LOG_LEVEL_INFO);

unsigned long last_time;

void setup() {
    last_time = millis();
}

void loop() {
    unsigned long time = millis();
    if (time > last_time + 10000) {
        Log.info("%d", (int) Time.now());
        if (time > last_time + 30000) {
            Log.warn("Time skip");
            RGB.control(true);
            RGB.color(255, 0, 0);
            while (1);
        }
        last_time = time;
    }
}

References

https://app.shortcut.com/particle/story/125902/millis-count-suddenly-jumps-3200-s-after-36-hours-of-use

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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)