nrf51dk bsp - Fix build when UARTs disabled.
Note: bit banger (UART 1) appears to be disabled for this BSP.
#include "hal/hal_flash.h"
#include "hal/hal_spi.h"
#include "hal/hal_i2c.h"
+#if MYNEWT_VAL(UART_0) || MYNEWT_VAL(UART_1)
#include "uart/uart.h"
+#endif
+#if MYNEWT_VAL(UART_0)
#include "uart_hal/uart_hal.h"
+#endif
#if MYNEWT_VAL(UART_0)
static struct uart_dev os_bsp_uart0;
