feather-stm32f405, feather-rp2040: add I2C pin names

src/machine/board_feather-stm32f405.go

@@ -231,6 +231,9 @@ const (
 
 	I2C_SDA_PIN = I2C0_SDA_PIN // default/primary I2C pins
 	I2C_SCL_PIN = I2C0_SCL_PIN //
+
+	SDA_PIN = I2C0_SDA_PIN
+	SCL_PIN = I2C0_SCL_PIN
 )
 
 var (

src/machine/board_feather_rp2040.go

@@ -38,6 +38,9 @@ const (
 
 	I2C1_SDA_PIN = GPIO2
 	I2C1_SCL_PIN = GPIO3
+
+	SDA_PIN = I2C1_SDA_PIN
+	SCL_PIN = I2C1_SCL_PIN
 )
 
 // SPI default pins