iot-lab_M3: set baud rate to 500 kbaud

The IoT-Lab testbed requires a baud rate of 500 kbaud to use UART.
Hence, this commit sets the default baud rate to this value and adapt
the `make term` target accordingly.

boards/iot-lab_M3/Makefile.include

@@ -39,7 +39,7 @@ export LINKFLAGS += -T$(LINKERSCRIPT)
 export OFLAGS = -O ihex
 export FFLAGS = $(HEXFILE)
 export DEBUGGER_FLAGS = $(RIOTBOARD)/$(BOARD)/dist/gdb.conf $(ELFFILE)
-export TERMFLAGS = -p $(PORT)
+export TERMFLAGS = -p $(PORT) -b 500000
 
 # use the nano-specs of the NewLib when available
 ifeq ($(shell $(LINK) -specs=nano.specs -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)

boards/iot-lab_M3/include/board.h

@@ -43,7 +43,7 @@ extern "C" {
  * @{
  */
 #define STDIO               UART_0
-#define STDIO_BAUDRATE      (115200U)
+#define STDIO_BAUDRATE      (500000U)
 #define STDIO_RX_BUFSIZE    (64U)
 /** @} */