CAN: Vector: Preserve the ESI flag on received frames

VectorCAN's CAN FD receive path copies the FD and BRS flags into
QCanBusFrame but drops the driver's error state indicator. Copy
that flag as well so applications can observe it.

[ChangeLog][CAN][VectorCAN] Received CAN FD frames now expose
the error state indicator reported by the driver.

Pick-to: 6.12 6.8
Assisted-by: OpenAI Codex
Change-Id: I2d68d5e3686bcf2f41b8830078c2d4204189d711
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>