boards: nucleo_l552ze_q: Fix green led port/pin definition

This commit fixes the definition of the green led pin
on the nucleo-L552ZE-Q board
The new port/pin for this led (LED1) can be confirmed
using docs from os.mbed.com for this board.
Additionally I tested it on my own hardware.
Also updated the LD2 entry in the docs which was incorrect.

Signed-off-by: Łukasz Hejnak (LeHack) <lehack-ghub@lehack.pl>