Staging: comedi: Fix coding style issues in ii_pci20kc.c

This patch fixes the following issues in file ii_pci20kc.c:

WARNING: please, no space before tabs
WARNING: unnecessary whitespace before a quoted newline
WARNING: line over 80 characters

Signed-off-by: Xenofon Foukas <foukas.xenofon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>