drivers/pinmux: stm32: Group gpio devices usability checks
drivers/pinmux: stm32: Group gpio devices usability checks

Move GPIO devices clock handling in stm32_pin_configure function
which is also used in stm32_setup_pins.
Additionally, add device usability check to be sure gpio driver
was initialized before being used by pinmux pseudo driver.

Last, going from the assumption that GPIO devices should be
initialized before being used by pinmux, then there is no need
to enable clock in case CONFIG_PM_DEVICE_RUNTIME=n.

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

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