Staging: comedi: fix multiple line dereference coding style issue in cb_pcidas64.c

This is a patch to the cb_pcidas64.c file that fixes up a multiple line
dereference warning found by the checkpatch.pl tool.

Signed-off-by: Jian Zhang <kernel@ubicomp.com.au>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>