drivers/pinmux: stm32: Control GPIO clock with central function

Use new gpio_stm32_clock_request function for GPIO clocks control.
To do this a new table of GPIO devices is set up at build time.
It is then used to populate targeted device when calling
gpio_stm32_clock_request.

Clean up remaining clock handling related code in the file.

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