drivers: ieee802154: rf2xx: Fix missing auto ACKs

The RF2XX driver not always sent ACK when a RX frame requests. This
happen because RF2XX transceiver asserts TRX_END interrupt after
confirm that the FCS is valid. The driver can now decode the frame
but in parallel the radio still processing the ACK frame. This will
sync the radio FSM state to ensure that ACK will be send.

Fixes #21659

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>