Staging: comedi: fix indent coding style issue in adl_pci9118.c

Patch to the adl_pci9118.c that fixes, ERROR: code indent should use tabs where possible, found by the checkpatch.pl tool

Signed-off-by: Maurice Dawson <mauricedawson2699@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>