staging:iio:meter:ade7758 switch from sw_ring to kfifo

sw ring is going away so switch over to kfifo based buffer implementation.
The only real change is that poll will return on some data there rather than
buffer 50% full.

Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/meter/Kconfig

···
 	tristate "Analog Devices ADE7758 Poly Phase Multifunction Energy Metering IC Driver"
 	depends on SPI
 	select IIO_TRIGGER if IIO_BUFFER
-	select IIO_SW_RING if IIO_BUFFER
+	select IIO_KFIFO_BUF if IIO_BUFFER
 	help
 	  Say yes here to build support for Analog Devices ADE7758 Polyphase
 	  Multifunction Energy Metering IC with Per Phase Information Driver.

drivers/staging/iio/meter/ade7758_ring.c

···
 #include <asm/unaligned.h>
 
 #include <linux/iio/iio.h>
-#include "../ring_sw.h"
+#include <linux/iio/kfifo_buf.h>
 #include <linux/iio/trigger_consumer.h>
 #include "ade7758.h"
 
···
 void ade7758_unconfigure_ring(struct iio_dev *indio_dev)
 {
 	iio_dealloc_pollfunc(indio_dev->pollfunc);
-	iio_sw_rb_free(indio_dev->buffer);
+	iio_kfifo_free(indio_dev->buffer);
 }
 
 int ade7758_configure_ring(struct iio_dev *indio_dev)
···
 	struct ade7758_state *st = iio_priv(indio_dev);
 	int ret = 0;
 
-	indio_dev->buffer = iio_sw_rb_allocate(indio_dev);
+	indio_dev->buffer = iio_kfifo_allocate(indio_dev);
 	if (!indio_dev->buffer) {
 		ret = -ENOMEM;
 		return ret;
···
 						 indio_dev->id);
 	if (indio_dev->pollfunc == NULL) {
 		ret = -ENOMEM;
-		goto error_iio_sw_rb_free;
+		goto error_iio_kfifo_free;
 	}
 
 	indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
···
 
 	return 0;
 
-error_iio_sw_rb_free:
-	iio_sw_rb_free(indio_dev->buffer);
+error_iio_kfifo_free:
+	iio_kfifo_free(indio_dev->buffer);
 	return ret;
 }