staging: comedi: amplc_pc236_common: Use 16-bit 0 for interrupt data

The Amplicon PC36AT/PCI236 common 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/20210223143055.257402-11-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ian-abbott

drivers/staging/comedi/drivers/amplc_pc236_common.c

@@ -126,7 +126,9 @@ static irqreturn_t pc236_interrupt(int irq, void *d)
 
 	handled = pc236_intr_check(dev);
 	if (dev->attached && handled) {
-		comedi_buf_write_samples(s, &s->state, 1);
+		unsigned short val = 0;
+
+		comedi_buf_write_samples(s, &val, 1);
 		comedi_handle_events(dev, s);
 	}
 	return IRQ_RETVAL(handled);