iio staging: fix cast warning

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/iio_simple_dummy_buffer.c

@@ -85,7 +85,7 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
 	}
 	/* Store the timestamp at an 8 byte aligned offset */
 	if (indio_dev->scan_timestamp)
-		*(s64 *)((phys_addr_t)data + ALIGN(len, sizeof(s64)))
+		*(s64 *)((u8 *)data + ALIGN(len, sizeof(s64)))
 			= iio_get_time_ns();
 	buffer->access->store_to(buffer, (u8 *)data, pf->timestamp);