soc: stm32l4: Factorize includes declarations for GPIO driver
soc: stm32l4: Factorize includes declarations for GPIO driver

Group #include declarations for CONFIG_GPIO_STM32


Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

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