Fix GPIOG usage of STM32L4 by activating VDDIO2 power supply

Author: pmancele

targets/TARGET_STM/gpio_api.c

@@ -73,6 +73,10 @@ GPIO_TypeDef *Set_GPIO_Clock(uint32_t port_idx) {
 #endif
 #if defined GPIOG_BASE
         case PortG:
+#if defined STM32L4
+            __HAL_RCC_PWR_CLK_ENABLE();
+            HAL_PWREx_EnableVddIO2();
+#endif
             gpio_add = GPIOG_BASE;
             __GPIOG_CLK_ENABLE();
             break;