staging: comedi: adl_pci6208: fix the ao_readback variable size

The 'ao_readback' variable in the private data struct is used to
cache the last value written to the analog output DAC channels.
The PCI-6208 has 8 analog output channels but the variable only
allowed space to cache 2 values.

Since the PCI-6216 board could be supported by this driver and
it has 16 analog outputs, create a define for the maximum number
of channels and use that to set the size of 'ao_readback'.

For now, set the max to 8 to save space since the PCI-6216 is
not currently supported.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/adl_pci6208.c

@@ -56,6 +56,8 @@ Configuration Options:
 #define PCI6208_DIO_DI_MASK		(0xf0)
 #define PCI6208_DIO_DI_SHIFT		(4)
 
+#define PCI6208_MAX_AO_CHANNELS		8
+
 struct pci6208_board {
 	const char *name;
 	unsigned short dev_id;
@@ -72,7 +74,7 @@ static const struct pci6208_board pci6208_boards[] = {
 
 struct pci6208_private {
 	struct pci_dev *pci_dev;
-	unsigned int ao_readback[2];
+	unsigned int ao_readback[PCI6208_MAX_AO_CHANNELS];
 };
 
 static int pci6208_ao_winsn(struct comedi_device *dev,