staging: Comedi: comedi_fops: Fixed the return error code

This patch fixes the checkpatch.pl warning:

WARNING: ENOSYS means 'invalid syscall nr' and nothing else

try_module_get fails when the reference count of the module is not
allowed to be incremented ,and hence -ENXIO is returned indicating
no device or address.

[IA - combined two of santhosh's changes to the error return value!]
Signed-off-by: santhosh pai <santhosh.pai88@yahoo.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -2606,7 +2606,7 @@ static int comedi_open(struct inode *inode, struct file *file)
 	}
 	if (dev->attached && dev->use_count == 0) {
 		if (!try_module_get(dev->driver->module)) {
-			rc = -ENOSYS;
+			rc = -ENXIO;
 			goto out;
 		}
 		if (dev->open) {