s390/qdio: clarify logical vs absolute in QIB's kerneldoc

qib.isliba and qib.osliba are actually logical addresses, and this is
also how the relevant code sets up these fields. Fix up the
documentation.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>