ath11k: move function ath11k_dp_rx_process_mon_status

Move the function below ath11k_dp_rx_mon_dest_process() and remove
the forward declaration.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-01179-QCAHKSWPL_SILICONZ-1
Signed-off-by: Aloka Dixit <quic_alokad@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220111032224.14093-2-quic_alokad@quicinc.com