very small spi comment update

Author: Jude Merritt

src/peripheral/spi.c

@@ -16,7 +16,7 @@
  * 
  * @file peripheral/spi.c
  * @authors Jude Merritt
- * @brief Implementation of SPI driver interface
+ * @brief Implementation of SPI driver
  */
 
 #include "peripheral/spi.h"

src/peripheral/spi.h

@@ -29,7 +29,7 @@
  **************************************************************************************************/
 
 /**
- * @brief Initialize an SPI interface.
+ * @brief Initialize an SPI instance.
  *
  * Prepares the specified SPI instance for communication. This must be called
  * before attempting any SPI transfers.