Standardize SAMD51 UART settings (#1155)

* machine/samd51: standardize samd51 uart settings

src/machine/board_pyportal.go

@@ -1,11 +1,7 @@
-// +build sam,atsamd51,pyportal
+// +build pyportal
 
 package machine
 
-import (
-	"device/sam"
-)
-
 // used to reset into bootloader
 const RESET_MAGIC_VALUE = 0xf01669ef
 
@@ -104,10 +100,10 @@ const (
 	USBCDC_DP_PIN = PA25
 )
 
-// TODO: add configuration for UART on SERCOM4 that is connected to TX/RX of ESP32
+// UART1 aka NINA_TX/NINA_RX
 const (
-	UART_TX_PIN = NoPin
-	UART_RX_PIN = NoPin
+	UART_TX_PIN = D1
+	UART_RX_PIN = D0
 )
 
 // I2C pins
@@ -116,14 +112,6 @@ const (
 	SCL_PIN = PB03 // SCL: SERCOM2/PAD[1]
 )
 
-// I2C on the PyPortal.
-var (
-	I2C0 = I2C{
-		Bus:    sam.SERCOM5_I2CM,
-		SERCOM: 5,
-	}
-)
-
 // SPI pins
 const (
 	SPI0_SCK_PIN  = PA13 // SCK: SERCOM1/PAD[1]
@@ -135,15 +123,6 @@ const (
 	NINA_SCK  = SPI0_SCK_PIN
 )
 
-// SPI on the PyPortal.
-var (
-	SPI0 = SPI{
-		Bus:    sam.SERCOM2_SPIM,
-		SERCOM: 2,
-	}
-	NINA_SPI = SPI0
-)
-
 // USB CDC identifiers
 const (
 	usb_STRING_PRODUCT      = "Adafruit PyPortal M4"