qcacmn: Make QDF NBUF history size configurable

Some of the targets require more QDF nbuf history
size, so making the size configurable keeping
default same.

Change-Id: Ic4ac43a1eacb1e58c0a05b794349525d614d7fc8
CRs-Fixed: 2929968

qdf/linux/src/qdf_nbuf.c

@@ -735,7 +735,9 @@ struct qdf_nbuf_event {
 	qdf_dma_addr_t iova;
 };
 
+#ifndef QDF_NBUF_HISTORY_SIZE
 #define QDF_NBUF_HISTORY_SIZE 4096
+#endif
 static qdf_atomic_t qdf_nbuf_history_index;
 static struct qdf_nbuf_event qdf_nbuf_history[QDF_NBUF_HISTORY_SIZE];