boards/common/stm32: Fix LED configuration
boards/common/stm32: Fix LED configuration

The inverted and non-inverted `LED<num>_ON` and `LED<num>_OFF` macros
are swapped. This didn't reveal in testing as the
`LED<num>_IS_INVERTED` macros where not properly evaluated, due to a
typo in the check. This fixes both.

kaspar030/RIOT,ant9000/RIOT,miri64/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,ant9000/RIOT,jasonatran/RIOT,miri64/RIOT,miri64/RIOT,kaspar030/RIOT,kYc0o/RIOT,jasonatran/RIOT,ant9000/RIOT,miri64/RIOT,miri64/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,jasonatran/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,kYc0o/RIOT