Merge pull request #1472 from c1728p9/nrf51_uart_glitch

Fix glitch when initializing NRF51-DK serial port

Author: 0xc0170

libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/serial_api.c

@@ -58,6 +58,8 @@ void serial_init(serial_t *obj, PinName tx, PinName rx) {
     obj->uart = (NRF_UART_Type *)uart;
 
     //pin configurations --
+    NRF_GPIO->OUT |= (1 << tx);
+    NRF_GPIO->OUT |= (1 << RTS_PIN_NUMBER);
     NRF_GPIO->DIR |= (1 << tx); //TX_PIN_NUMBER);
     NRF_GPIO->DIR |= (1 << RTS_PIN_NUMBER);