drivers: can: rename can_state enumerations

Rename the can_state enumerations to contain the word STATE to make their
meaning more clear:
- CAN_ERROR_ACTIVE  => CAN_STATE_ERROR_ACTIVE
- CAN_ERROR_WARNING => CAN_STATE_ERROR_WARNING
- CAN_ERROR_PASSIVE => CAN_STATE_ERROR_PASSIVE
- CAN_BUS_OFF       => CAN_STATE_BUS_OFF

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>