boards/common/arduino-zero: Add Arudino SPI mapping

The Arduino Zero based boards already provided the feature
`arduino_spi`, but were missing the corresponding mapping. This fixes
the issue by adding the SPI bus numbers for the ISP SPI bus and the
D11D12D13 SPI bus.

(And in order to actually add the D11D12D13 SPI bus, the `periph_conf.h`
was extended to provide an SPI configuration for it.)

boards/common/arduino-zero/include/arduino_iomap.h

@@ -139,6 +139,20 @@ extern "C" {
 #define ARDUINO_PIN_9_PWM_CHAN  1
 /** @} */
 
+/**
+ * @name    Arduino's SPI buses
+ * @{
+ */
+/**
+ * @brief   SPI_DEV(0) is connected to the ISP
+ */
+#define ARDUINO_SPI_ISP         SPI_DEV(0)
+/**
+ * @brief   SPI_DEV(1) is connected to D11/D12/D13
+ */
+#define ARDUINO_SPI_D11D12D13   SPI_DEV(1)
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif

boards/common/arduino-zero/include/periph_conf.h

@@ -241,6 +241,18 @@ static const spi_conf_t spi_config[] = {
         .miso_pad = SPI_PAD_MISO_0,
         .mosi_pad = SPI_PAD_MOSI_2_SCK_3,
         .gclk_src = SAM0_GCLK_MAIN,
+    },
+    {
+        .dev      = &SERCOM1->SPI,
+        .miso_pin = GPIO_PIN(PA, 19),
+        .mosi_pin = GPIO_PIN(PA, 16),
+        .clk_pin  = GPIO_PIN(PA, 17),
+        .miso_mux = GPIO_MUX_C,
+        .mosi_mux = GPIO_MUX_C,
+        .clk_mux  = GPIO_MUX_C,
+        .miso_pad = SPI_PAD_MISO_3,
+        .mosi_pad = SPI_PAD_MOSI_0_SCK_1,
+        .gclk_src = SAM0_GCLK_MAIN,
     }
 };