dts: bindings: fix stm32 UART base include file
dts: bindings: fix stm32 UART base include file

Include files should not have compatible properties set. These do not
represent real hardware and should therefore not appear to do so, e.g.
by appearing in the bindings index as if they were a real hardware
peripheral.

Signed-off-by: Martí Bolívar <9d90ac4c7bf6a305f6bfd81a23c7859bc883380e@nordicsemi.no>

finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr