ath11k: Refactor the peer delete

Introduce new helper function for peer delete to reuse this logic
in all peer cleanup procedures. Found this in code review.
Also this change is applicable for all the platform.

Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.5.0.1-01067-QCAHKSWPL_SILICONZ-1

Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/1646024079-26391-1-git-send-email-quic_periyasa@quicinc.com