fix nrf52dk build - soft_pwm should be conditional
#if MYNEWT_VAL(PWM)
#include <pwm_nrf52/pwm_nrf52.h>
#endif
+#if MYNEWT_VAL(SOFT_PWM)
#include <soft_pwm/soft_pwm.h>
+#endif
#if MYNEWT_VAL(UART_0)
static struct uart_dev os_bsp_uart0;
