[conf] fix some example GLS_APPROACH defines
[stm32] spektrum for F4

Not tested on an actual F4 board!
Using some of the new gpio helper functions.
Also removed seemingly useless DebugInit.
[stm32][i2c] pin configuration in board files

Use the gpio_enable_clock helper function.
Also remove the unused scl_pin and sda_pin variables in the i2c struct.
[conf][stm32] spektrum defines for Lisa/L
[stm32][conf] fix UART1_GPIO_RX on lisa/m
[stm32] i2c3 for stm32f4, untested
[stm32][ppm] config cleanup