atsamd: Add support for programming SERCOM pins

Signed-off-by: Florian Heilmann <Florian.Heilmann@gmx.net>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/atsamd/gpio.h

@@ -37,6 +37,7 @@ uint16_t gpio_adc_read(struct gpio_adc g);
 void gpio_adc_cancel_sample(struct gpio_adc g);
 
 struct spi_config {
+    void *ss;
     uint32_t ctrla, baud;
 };
 struct spi_config spi_setup(uint32_t bus, uint8_t mode, uint32_t rate);
@@ -45,6 +46,7 @@ void spi_transfer(struct spi_config config, uint8_t receive_data
                   , uint8_t len, uint8_t *data);
 
 struct i2c_config {
+    void *si;
     uint8_t addr;
 };