s390/uv: Fix handling of length extensions

commit 27dc0700 upstream.

The query parameter block might contain additional information and can
be extended in the future. If the size of the block does not suffice we
get an error code of rc=0x100.  The buffer will contain all information
up to the specified size and the hypervisor/guest simply do not need the
additional information as they do not know about the new data.  That
means that we can (and must) accept rc=0x100 as success.

Cc: stable@vger.kernel.org
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Fixes: 5abb9351 ("s390/uv: introduce guest side ultravisor code")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>