boards: removed some superfluous definitions

- removed UART_STDIO_DEV as they use the default value
- removed BTN_B1_PIN for nucleo-207, as its already defined in the common header

boards/arduino-mega2560/include/board.h

@@ -28,11 +28,6 @@
 extern "C" {
 #endif
 
-/**
- * @brief Use the UART 0 for STDIO on this board
- */
-#define UART_STDIO_DEV      UART_DEV(0)
-
 /**
 * @brief As the CPU is too slow to handle 115200 baud, we set the default
 *        baudrate to 9600 for this board

boards/nucleo-f207/include/board.h

@@ -27,6 +27,7 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+
 /**
  * @brief   LED pin definitions and handlers
  * @{
@@ -56,16 +57,6 @@ extern "C" {
 #define LED2_TOGGLE         (GPIOB->ODR  ^= LED2_MASK)
 /** @} */
 
-/**
- * @brief Use the 1st UART for STDIO on this board
- */
-#define UART_STDIO_DEV      UART_DEV(0)
-
-/**
- * @brief   User button
- */
-#define BTN_B1_PIN          GPIO_PIN(PORT_C, 13)
-
 /**
  * @brief   Initialize board specific hardware, including clock, LEDs and std-IO
  */

boards/z1/include/board.h

@@ -54,15 +54,6 @@ extern "C" {
 #define XTIMER_BACKOFF              (40)
 /** @} */
 
-/**
- * @brief   Standard input/output device configuration
- * @{
- */
-#define UART_STDIO_DEV              (UART_DEV(0))
-#define UART_STDIO_BAUDRATE         (115200U)
-#define UART_STDIO_RX_BUFSIZE       (64U)
-/** @} */
-
 /**
  * @brief   CPU core configuration
  *