wifi: ath12k: fix incorrect handling of AMSDU frames

When a data traffic with size greater than 1500 is initiated,
say size 65500, it is sent as a set of AMSDUs (3 MSDUs)
in a MPDU.

These AMSDUs are incorrectly classified as multicast
and peer id gets changed, except for first msdu,
because of mcast_bcast bit derived from rx_desc
for every msdu received.

The mcast_bcast bit in rx_desc is only valid for
first msdu. Hence, add changes to derive mcast_bcast
only if it is a first msdu.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Signed-off-by: Harshitha Prem <quic_hprem@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230320090400.30027-1-quic_hprem@quicinc.com