tty: serial: fsl_lpuart: remove sg_set_buf() for sport->rx_sgl

Since .sg_init_one() already set sg entry page like below code.
	sg_init_one()
		sg_init_table(sg, 1);
		sg_set_buf(sg, buf, buflen);

So it should not set sg entry page again, remove the redundant code.
Signed-off-by: NFugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20190717051930.15514-5-fugang.duan@nxp.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -1102,7 +1102,6 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
 		return -ENOMEM;
 
 	sg_init_one(&sport->rx_sgl, ring->buf, sport->rx_dma_rng_buf_len);
-	sg_set_buf(&sport->rx_sgl, ring->buf, sport->rx_dma_rng_buf_len);
 	nent = dma_map_sg(sport->port.dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE);
 
 	if (!nent) {