s390x/ipl: fix reboots for migration from different bios

s390x/ipl: fix reboots for migration from different bios

When migrating from a different QEMU version, the start_address and
bios_start_address may differ. During migration these values are migrated
and overwrite the values that were detected by QEMU itself.

On a reboot, QEMU will reload its own BIOS, but use the migrated start
addresses, which does not work if the values differ.

Fix this by not relying on the migrated values anymore, but still
provide them during migration, so existing QEMUs continue to work.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
(cherry picked from commit bb0995468a39f14077ceaa8ed5afdca849f00c7c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>