mwifiex: fix 'Smatch' warnings

Following three warnings are fixed:

>init.c +256 mwifiex_init_adapter(71)
>warn: variable dereferenced before check 'adapter->sleep_cfm'
>(see line 191)

>sta_rx.c +193 mwifiex_process_sta_rx_packet(75)
>warn: variable dereferenced before check 'priv' (see line 182)

Signed-off-by: Yogesh Ashok Powar <yogeshp@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/init.c b/drivers/net/wireless/mwifiex/init.c
index d792b3f..2694045 100644
--- a/drivers/net/wireless/mwifiex/init.c
+++ b/drivers/net/wireless/mwifiex/init.c
@@ -187,8 +187,6 @@
 	struct mwifiex_opt_sleep_confirm *sleep_cfm_buf = NULL;
 
 	skb_put(adapter->sleep_cfm, sizeof(struct mwifiex_opt_sleep_confirm));
-	sleep_cfm_buf = (struct mwifiex_opt_sleep_confirm *)
-						(adapter->sleep_cfm->data);
 
 	adapter->cmd_sent = false;
 
@@ -254,6 +252,8 @@
 	mwifiex_wmm_init(adapter);
 
 	if (adapter->sleep_cfm) {
+		sleep_cfm_buf = (struct mwifiex_opt_sleep_confirm *)
+						adapter->sleep_cfm->data;
 		memset(sleep_cfm_buf, 0, adapter->sleep_cfm->len);
 		sleep_cfm_buf->command =
 				cpu_to_le16(HostCmd_CMD_802_11_PS_MODE_ENH);