qcacmn: remove bss and self peer back pointers from dp_vdev

Remove self and BSS peer back pointers and added APIs to
get self and BSS peer from VDEV

These new APIs will iterate through peer list and return
the appropriate peer by taking a reference

Caller has to take care of releasing the reference

Change-Id: I550ff83d665f3ad0a185bea1a1e6270c5474ff07

dp/wifi3.0/dp_peer.h

@@ -401,4 +401,8 @@ static inline void dp_peer_ext_stats_ctx_dealloc(struct dp_soc *soc,
 }
 #endif
 
+struct dp_peer *dp_vdev_bss_peer_ref_n_get(struct dp_soc *soc,
+					   struct dp_vdev *vdev);
+struct dp_peer *dp_sta_vdev_self_peer_ref_n_get(struct dp_soc *soc,
+						struct dp_vdev *vdev);
 #endif /* _DP_PEER_H_ */