esp: fix setting of ESPState mig_version_id when launching QEMU with -S option

esp: fix setting of ESPState mig_version_id when launching QEMU with -S option

If QEMU is launched with the -S option then the ESPState mig_version_id property
is left unset due to the ordering of the VMState fields in the VMStateDescription
for sysbusespscsi and pciespscsi. If the VM is migrated and restored in this
stopped state, the version tests in the vmstate_esp VMStateDescription and
esp_post_load() become confused causing the migration to fail.

Fix the ordering problem by moving the setting of mig_version_id to a common
esp_pre_save() function which is invoked first by both sysbusespscsi and
pciespscsi rather than at the point where ESPState is itself serialised into the
migration stream.

Buglink: https://bugs.launchpad.net/qemu/+bug/1922611
Fixes: 0bd005be78 ("esp: add vmstate_esp version to embedded ESPState")
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210407124842.32695-1-mark.cave-ayland@ilande.co.uk>