s390/ipl: fix off-by-one in update_machine_ipl_properties()

s390/ipl: fix off-by-one in update_machine_ipl_properties()

In update_machine_ipl_properties() the array ascii_loadparm needs to
hold the 8 char loadparm and a string terminating zero char.

Let's increase the size of ascii_loadparm accordingly.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Fixes: 0a01e082a428 ("s390/ipl: sync back loadparm")
Fixes: Coverity CID 1421966
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200320143101.41764-1-pasic@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>