Toggle should use output register, not pin state

[tombrazier]

See discussion in MarlinFirmware/Marlin#27341.

Function pin_type::toggle() reads a value from gpio_reg().reg_control (known as FIOPIN in the LPC1768 manual chapter 9), modifies it and then writes it back to gpio_reg().reg_control. On writing, this updates the output register for GPIO. However the value read actually reads the pin state, not the output register.

It is possible when toggling pins in quick succession for a race condition to exist where a pin's output state is still reading an old value when gpio_reg().reg_control is read, resulting in lost pin changes.

To read the output register, one must read gpio_reg().reg_set (FIOSET in the LPC1768 manual).

I am not able to test this PR because I do not have an LPC1768 board but I have a report from MarlinFirmware/Marlin#27341 that it works.

[tombrazier]

I now have multiple reports of this PR fixing the issue in Marlin.

[p3p]

Thanks I will get this merged and a release done as soon as I can