Contribution description

During tests of stm32f469i-disco I noticed that LEDX_ON and LEDX_OFF macros are mismatched.

When I looked at board manual I found that in this board LEDs are on using low signal - 4.15 Buttons and LEDs, "To light a LED a low logic state 0 should be written in the corresponding GPIO". Most (all?) STM Nucleo boards use for this purpose high signal, for example, the f429zi, 6.5 LEDs, "These user LEDs are on when the I/O is HIGH value, and are off when the I/O is LOW."

This PR fix this issue.

Testing procedure

Without PR, this sample program switch all four LEDs on.

#include "led.h"

int main(void)
{
 LED0_OFF;
 LED1_OFF;
 LED2_OFF;
 LED3_OFF;

 return 0;
}

With this PR everything is OK - LEDs remain off.

Issues/PRs references

None