qcacmn: Add memory stats pertaining to DP usage

Add sysfs node for DP level memory stats:
/sys/kernel/wifi/wlan/wlan_dp_mem_stats
These include Tx, Rx SKB memory allocated, Tx/Rx
buffer count, outstanding Tx desc count.
Add and subtract the skb memory for Rx/Tx when
the map/unmap functions are invoked.

Change-Id: If62cc47bb60f7eb63f60e861f755f3417248677f
CRs-Fixed: 2724482

qdf/inc/qdf_nbuf.h

@@ -1702,12 +1702,7 @@ static inline qdf_nbuf_t
 qdf_nbuf_alloc_fl(qdf_device_t osdev, qdf_size_t size, int reserve, int align,
 		  int prio, const char *func, uint32_t line)
 {
-	qdf_nbuf_t nbuf;
-
-	nbuf = __qdf_nbuf_alloc(osdev, size, reserve, align, prio, func, line);
-	if (qdf_likely(nbuf))
-		qdf_mem_skb_inc(nbuf->truesize);
-	return nbuf;
+	return __qdf_nbuf_alloc(osdev, size, reserve, align, prio, func, line);
 }
 
 /**
@@ -1727,14 +1722,7 @@ static inline qdf_nbuf_t
 qdf_nbuf_alloc_no_recycler_fl(size_t size, int reserve, int align,
 			      const char *func, uint32_t line)
 {
-	qdf_nbuf_t nbuf;
-
-	nbuf = __qdf_nbuf_alloc_no_recycler(size, reserve, align, func, line);
-
-	if (qdf_likely(nbuf))
-		qdf_mem_skb_inc(nbuf->truesize);
-
-	return nbuf;
+	return __qdf_nbuf_alloc_no_recycler(size, reserve, align, func, line);
 }
 
 static inline void qdf_nbuf_free(qdf_nbuf_t buf)