We use lazy allocation for translation table entries but don't handle
allocation (and other) failures during translation table updates.

Handle these failures and undo translation table updates when it's
meaningful.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>