vfio/cpr-legacy: drop an erroneous assert

vfio/cpr-legacy: drop an erroneous assert

vfio_legacy_cpr_dma_map() is not only used in post_load on destination
but also error recovery path on source side. Assert it for destination
is wrong.

Fixes: 7e9f21411302 ("vfio/container: restore DMA vaddr")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
Link: https://lore.kernel.org/qemu-devel/20250928085432.40107-3-zhenzhong.duan@intel.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>