wifi: ath12k: remove invalid peer create logic

In ath12k_mac_op_assign_vif_chanctx(), there is a logic to
create peer using ar->mac_addr for a STA vdev. This is invalid
because a STA vdev should have a peer created using AP's
MAC address. Besides, if we run into that logic, it means a peer
has already been created earlier, we should not create it again.
So remove it.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Kang Yang <quic_kangyang@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240429081525.983-6-quic_kangyang@quicinc.com