drivers: gpio: stm32: Apply GPIOG specific code to U5 series

In STM32U5 as well it is required to enable VDD before use.
Difference is that U5 enables this under PWR_SVMCR_IO2SV flag.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
(cherry picked from commit e1cb0845)