Revert "serial: pl011: use DMA RX polling by default"

This reverts commit 17438217a6f5e33d920ed3821a4b857311cc2872 on request
of Linus Walleij:
	Greg can you please drop or revert
	commit 17438217a6f5e33d920ed3821a4b857311cc2872
	"serial: pl011: use DMA RX polling by default"
	from the TTY tree until this has been sorted out?

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/amba-pl011.c

@@ -325,7 +325,7 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *
 		dmaengine_slave_config(chan, &rx_conf);
 		uap->dmarx.chan = chan;
 
-		if (plat) {
+		if (plat && plat->dma_rx_poll_enable) {
 			/* Set poll rate if specified. */
 			if (plat->dma_rx_poll_rate) {
 				uap->dmarx.auto_poll_rate = false;

include/linux/amba/serial.h

@@ -203,6 +203,7 @@ struct amba_pl011_data {
 	bool (*dma_filter)(struct dma_chan *chan, void *filter_param);
 	void *dma_rx_param;
 	void *dma_tx_param;
+	bool dma_rx_poll_enable;
 	unsigned int dma_rx_poll_rate;
 	unsigned int dma_rx_poll_timeout;
         void (*init) (void);