mwifiex: fix potential out-of-boundary access to ibss rate table

smatch found this error:

CHECK   drivers/net/wireless/mwifiex/join.c
  drivers/net/wireless/mwifiex/join.c:1121
  mwifiex_cmd_802_11_ad_hoc_join()
  error: testing array offset 'i' after use.

Cc: <stable@vger.kernel.org> # 3.0+
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwifiex/join.c

@@ -1117,10 +1117,9 @@ mwifiex_cmd_802_11_ad_hoc_join(struct mwifiex_private *priv,
 		adhoc_join->bss_descriptor.bssid,
 		adhoc_join->bss_descriptor.ssid);
 
-	for (i = 0; bss_desc->supported_rates[i] &&
-			i < MWIFIEX_SUPPORTED_RATES;
-			i++)
-			;
+	for (i = 0; i < MWIFIEX_SUPPORTED_RATES &&
+		    bss_desc->supported_rates[i]; i++)
+		;
 	rates_size = i;
 
 	/* Copy Data Rates from the Rates recorded in scan response */