staging: comedi: ni_6527: Use 16-bit 0 for interrupt data

The ni_6527 driver has an "interrupt" subdevice that supports Comedi
asynchronous commands, placing a value in the Comedi buffer for each
interrupt.  The subdevice uses Comedi's 16-bit sample format but the
interrupt handler is calling `comedi_buf_write_samples()` with the
address of a 32-bit integer `&s->state`.  On bigendian machines, this
will copy 2 bytes from the wrong end of the 32-bit integer.  This isn't
really a problem since `s->state` will always be 0 for this subdevice,
but clean it up by using a 16-bit variable initialized to 0 to pass the
value.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-13-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ian-abbott

drivers/staging/comedi/drivers/ni_6527.c

@@ -195,7 +195,9 @@ static irqreturn_t ni6527_interrupt(int irq, void *d)
 		return IRQ_NONE;
 
 	if (status & NI6527_STATUS_EDGE) {
-		comedi_buf_write_samples(s, &s->state, 1);
+		unsigned short val = 0;
+
+		comedi_buf_write_samples(s, &val, 1);
 		comedi_handle_events(dev, s);
 	}