iio:dummy: Stop enabling timestamp by default.

It's bad practice and only done in this fake driver + it breaks my
attempt to take struct buffer opaque. Not worth an access function
as it shouldn't be done anyway.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

drivers/iio/dummy/iio_simple_dummy_buffer.c

@@ -132,9 +132,6 @@ int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 
 	iio_device_attach_buffer(indio_dev, buffer);
 
-	/* Enable timestamps by default */
-	buffer->scan_timestamp = true;
-
 	/*
 	 * Tell the core what device type specific functions should
 	 * be run on either side of buffer capture enable / disable.