boards: cleanup serial RX DMA hrt_call_every

- remove ts_to_abstime dependency

boards/av/x-v1/src/init.c

@@ -161,22 +161,11 @@ __EXPORT int board_app_initialize(uintptr_t arg)
 		syslog(LOG_ERR, "[boot] DMA alloc FAILED\n");
 	}
 
-	/* set up the serial DMA polling */
+#if defined(SERIAL_HAVE_RXDMA)
+	// set up the serial DMA polling at 1ms intervals for received bytes that have not triggered a DMA event.
 	static struct hrt_call serial_dma_call;
-	struct timespec ts;
-
-	/*
-	 * Poll at 1ms intervals for received bytes that have not triggered
-	 * a DMA event.
-	 */
-	ts.tv_sec = 0;
-	ts.tv_nsec = 1000000;
-
-	hrt_call_every(&serial_dma_call,
-		       ts_to_abstime(&ts),
-		       ts_to_abstime(&ts),
-		       (hrt_callout)stm32_serial_dma_poll,
-		       NULL);
+	hrt_call_every(&serial_dma_call, 1000, 1000, (hrt_callout)stm32_serial_dma_poll, NULL);
+#endif
 
 	(void) board_hardfault_init(2, true);