staging: dgap: fix the rest of the checkpatch warnings in dgap.c

This patch fixes all the simple_strtol and simple_strtoul warnings
as reported by checkpatch. After this patch, checkpatch will report
zero errors or warnings on dgap.c.

Signed-off-by: Mark Hounschell <markh@compro.net>
Tested-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>