drivers: can: mcux: Fix can_detach

The detach function didn't call FLEXCAN_TransferAbortReceive.
The state of the mailbox after detaching was still kFLEXCAN_StateRxData
and therefore a new filter couldn't be attached.
This PR calls FLEXCAN_TransferAbortReceive and releases the mailbox.

Signed-off-by: Alexander Wachter <alexander.wachter@student.tugraz.at>