serial: pl011: Allocate TX DMA buffer from DMA capable memory

Allocating with __GFP_DMA avoids the need for bounce buffers
Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/amba-pl011.c

@@ -988,7 +988,7 @@ static void pl011_dma_startup(struct uart_amba_port *uap)
 	if (!uap->dmatx.chan)
 		return;
 
-	uap->dmatx.buf = kmalloc(PL011_DMA_BUFFER_SIZE, GFP_KERNEL);
+	uap->dmatx.buf = kmalloc(PL011_DMA_BUFFER_SIZE, GFP_KERNEL | __GFP_DMA);
 	if (!uap->dmatx.buf) {
 		dev_err(uap->port.dev, "no memory for DMA TX buffer\n");
 		uap->port.fifosize = uap->fifosize;