Extend the delay ensure post reset pulse delayed.
Extend the delay ensure post reset pulse delayed.

Given the original poster's comment that "It happens very consistently for us." I suspect the motor spin observed in https://github.com/PX4/Firmware/issues/7457 is not caused by the original issue of slow decay on the PWM pins at reset, but the post reset pulse of 3.1 Ms arriving in a window that the ESC considers it valid.

The results from testing, indicated that the if the PWM pins were clamped low for > 300 Ms, prior to reset the motors did not spin. This would delay the the post reset pulse of 3.1 Ms out by > 300 Ms. 

This change delays the reset and therefore the pulse by at least 400 Ms.
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