qcacld-3.0: Cleanup fastpath changes

Do following cleanup on fastpath code changes:
1) Remove reaping of Tx HIF buffers in Rx handling, instead handle
   reaping in Tx fastpath itself.
2) In ce_per_engine_service_fast check for more Rx packets after
   packet processing.
3) Make stub functions as static inline for non-fastpath enabled case.

Change-Id: If07c4344a424ce13b94128bf28931a24255b661a
CRs-Fixed: 987182

uapi/linux/osapi_linux.h

@@ -231,6 +231,7 @@ void a_netbuf_queue_init(A_NETBUF_QUEUE_T *q);
 #include "ath_carr_pltfrm.h"
 #endif /* QCA_PARTNER_PLATFORM */
 
+#define SLOTS_PER_DATAPATH_TX 2
 #else                           /* __KERNEL__ */
 
 #ifdef __GNUC__