Add a mechanism for sending multi-part messages to the I2C driver base class.

apps/drivers/device/i2c.h

@@ -100,6 +100,16 @@ protected:
 	int		transfer(const uint8_t *send, unsigned send_len,
 				 uint8_t *recv, unsigned recv_len);
 
+	/**
+	 * Perform a multi-part I2C transaction to the device.
+	 *
+	 * @param msgv		An I2C message vector.
+	 * @param msgs		The number of entries in the message vector.
+	 * @return		OK if the transfer was successful, -errno
+	 *			otherwise.
+	 */
+	int		transfer(i2c_msg_s *msgv, unsigned msgs);
+
 	/**
 	 * Change the bus address.
 	 *