qcacmn: Initialize only 1 RXDMA DST ring for WCN7850

WCN7850 has only one RXDMA DST ring, as opposed to other
lithium family chipsets, which had 2 RXDMA DST ring.

Refactor the code to pick the number of rxdma destination
rings from CFG context.

Change-Id: I20d475c02690043e969bc7a78605809b8c6814ae
CRs-Fixed: 3084440

wlan_cfg/wlan_cfg.h

@@ -404,6 +404,7 @@ struct wlan_cfg_dp_soc_ctxt {
 	bool vdev_stats_hw_offload_config;
 	int vdev_stats_hw_offload_timer;
 #endif
+	uint8_t num_rxdma_dst_rings_per_pdev;
 };
 
 /**