mwifiex: CPU mips optimization with NO_PKT_PRIO_TID

If we go through the entire for loop in
mwifiex_wmm_get_highest_priolist_ptr() and don't find any packets,
set highest_queued_prio to NO_PKT_PRIO_TID (< LOW_PRIO_TID).

Signed-off-by: Marc Yang <yangyang@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/mwifiex/main.h b/drivers/net/wireless/mwifiex/main.h
index ea3184d..3154b0a 100644
--- a/drivers/net/wireless/mwifiex/main.h
+++ b/drivers/net/wireless/mwifiex/main.h
@@ -202,6 +202,7 @@
 #define WMM_HIGHEST_PRIORITY		7
 #define HIGH_PRIO_TID				7
 #define LOW_PRIO_TID				0
+#define NO_PKT_PRIO_TID				(-1)
 
 struct mwifiex_wmm_desc {
 	struct mwifiex_tid_tbl tid_tbl_ptr[MAX_NUM_TID];