hw/core/qdev-properties-system: Add missing return in set_drive_helper()

hw/core/qdev-properties-system: Add missing return in set_drive_helper()

Currently, changing the 'drive' property of e.g. a scsi-hd object will
result in an assertion failure if the aio context of the block node
it's replaced with doesn't match the current aio context:

> bdrv_replace_child_noperm: Assertion `bdrv_get_aio_context(old_bs) ==
> bdrv_get_aio_context(new_bs)' failed.

The problematic scenario is already detected, but a 'return' statement
was missing.

Cc: qemu-stable@nongnu.org
Fixes: d1a58c176a ("qdev: allow setting drive property for realized device")
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250523070211.280498-1-f.ebner@proxmox.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>