pc-bios/s390x: Initialize machine loadparm before probing IPL devices

pc-bios/s390x: Initialize machine loadparm before probing IPL devices

Commit bb185de423 ("s390x: Add individual loadparm assignment to
CCW device") allowed boot devices to be assigned a loadparm value independent
of the machine value, however, when no boot devices are defined, the machine
loadparm becomes ignored. Therefore, let's check the machine loadparm
prior to probing the devices.

Signed-off-by: Jared Rossi <jrossi@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20241114161952.3508554-1-jrossi@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>