qcacmn: Do not use WBM2SW4 as tx completion ring

Ageout flush does not happen for WBM2SW4 if there
is only one TX completion pending in FIFO and all the
other WBM release rings are not active. This is due to
an issue in HW and this prevents suspend to happen due
to pending tx completions.

Fix is to avoid using WBM2SW4 release ring and instead
reuse WBM2SW0.

Change-Id: I250d8c9d460895449939212ebdb7abd62edb0234
CRs-Fixed: 3124733

dp/wifi3.0/dp_internal.h

@@ -41,6 +41,8 @@
 /* Macro For NYSM value received in VHT TLV */
 #define VHT_SGI_NYSM 3
 
+#define INVALID_WBM_RING_NUM 0xFF
+
 /* struct htt_dbgfs_cfg - structure to maintain required htt data
  * @msg_word: htt msg sent to upper layer
  * @m: qdf debugfs file pointer