tty: serial: fsl_lpuart: use GFP_ATOMIC under spin lock

The function lpuart_start_rx_dma() is called from several
places, in some of which, such as lpuart_startup(), a lock
be held here, so we should use GFP_ATOMIC when a lock is held.

Fixes: 5887ad4 ("tty: serial: fsl_lpuart: Use cyclic DMA for Rx")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -852,7 +852,7 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
 	if (sport->rx_dma_rng_buf_len < 16)
 		sport->rx_dma_rng_buf_len = 16;
 
-	ring->buf = kmalloc(sport->rx_dma_rng_buf_len, GFP_KERNEL);
+	ring->buf = kmalloc(sport->rx_dma_rng_buf_len, GFP_ATOMIC);
 	if (!ring->buf) {
 		dev_err(sport->port.dev, "Ring buf alloc failed\n");
 		return -ENOMEM;