Added less used USART3 config for l4x5 and l4x6 (#150)

* Added serial setup

* fmt

* comma

Author: unizippro

src/serial.rs

@@ -76,6 +76,9 @@ use crate::gpio::gpiob::PB5;
 #[cfg(any(feature = "stm32l4x5", feature = "stm32l4x6",))]
 use crate::gpio::gpioc::PC12;
 
+#[cfg(any(feature = "stm32l4x5", feature = "stm32l4x6",))]
+use crate::gpio::gpiod::{PD8, PD9};
+
 #[cfg(any(feature = "stm32l4x5", feature = "stm32l4x6",))]
 use crate::gpio::AF8;
 
@@ -436,6 +439,11 @@ pins! {
     USART3: (PC10, PC11, PD12, AF7),
 }
 
+#[cfg(any(feature = "stm32l4x5", feature = "stm32l4x6",))]
+pins! {
+    USART3: (PD8, PD9, PB1, PA6, AF7),
+}
+
 // UART 4
 #[cfg(any(feature = "stm32l4x5", feature = "stm32l4x6",))]
 pins! {