Add spi_pinmap_t struct

hal/spi_api.h

@@ -51,7 +51,17 @@ typedef struct {
  */
 typedef struct spi_s spi_t;
 
-#endif
+typedef struct {
+    const int peripheral;
+    const PinName mosi_pin;
+    const int mosi_function;
+    const PinName miso_pin;
+    const int miso_function;
+    const PinName sclk_pin;
+    const int sclk_function;
+    const PinName ssel_pin;
+    const int ssel_function;
+} spi_pinmap_t;
 
 /**
  * Describes the capabilities of a SPI peripherals