staging: comedi: addi_apci_1032: Fix endian problem for COS sample

The Change-Of-State (COS) subdevice supports Comedi asynchronous
commands to read 16-bit change-of-state values.  However, the interrupt
handler is calling `comedi_buf_write_samples()` with the address of a
32-bit integer `&s->state`.  On bigendian architectures, it will copy 2
bytes from the wrong end of the 32-bit integer.  Fix it by transferring
the value via a 16-bit integer.

Fixes: 6bb45f2 ("staging: comedi: addi_apci_1032: use comedi_buf_write_samples()")
Cc: <stable@vger.kernel.org> # 3.19+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-2-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ian-abbott

drivers/staging/comedi/drivers/addi_apci_1032.c

@@ -260,6 +260,7 @@ static irqreturn_t apci1032_interrupt(int irq, void *d)
 	struct apci1032_private *devpriv = dev->private;
 	struct comedi_subdevice *s = dev->read_subdev;
 	unsigned int ctrl;
+	unsigned short val;
 
 	/* check interrupt is from this device */
 	if ((inl(devpriv->amcc_iobase + AMCC_OP_REG_INTCSR) &
@@ -275,7 +276,8 @@ static irqreturn_t apci1032_interrupt(int irq, void *d)
 	outl(ctrl & ~APCI1032_CTRL_INT_ENA, dev->iobase + APCI1032_CTRL_REG);
 
 	s->state = inl(dev->iobase + APCI1032_STATUS_REG) & 0xffff;
-	comedi_buf_write_samples(s, &s->state, 1);
+	val = s->state;
+	comedi_buf_write_samples(s, &val, 1);
 	comedi_handle_events(dev, s);
 
 	/* enable the interrupt */