rtlwifi: Fix smatch warnings in usb.c

Smatch displays the following:
  CHECK   drivers/net/wireless/rtlwifi/usb.c
drivers/net/wireless/rtlwifi/usb.c:458 _rtl_usb_rx_process_agg() warn: assigning (-98) to unsigned variable 'stats.noise'
drivers/net/wireless/rtlwifi/usb.c:503 _rtl_usb_rx_process_noagg() warn: assigning (-98) to unsigned variable 'stats.noise'
drivers/net/wireless/rtlwifi/usb.c:596 _rtl_rx_get_padding() info: ignoring unreachable code.
drivers/net/wireless/rtlwifi/usb.c:596 _rtl_rx_get_padding() info: ignoring unreachable code.

The variable 'stats.noise' is not used, thus the initializers are removed.
The unreachable code info is fixed by including the appropriate section inside
#ifdef .. #endif constructions.
Signed-off-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/usb.c

@@ -455,7 +455,6 @@ static void _rtl_usb_rx_process_agg(struct ieee80211_hw *hw,
 	struct ieee80211_rx_status rx_status = {0};
 	struct rtl_stats stats = {
 		.signal = 0,
-		.noise = -98,
 		.rate = 0,
 	};
 
@@ -498,7 +497,6 @@ static void _rtl_usb_rx_process_noagg(struct ieee80211_hw *hw,
 	struct ieee80211_rx_status rx_status = {0};
 	struct rtl_stats stats = {
 		.signal = 0,
-		.noise = -98,
 		.rate = 0,
 	};
 
@@ -582,12 +580,15 @@ static void _rtl_rx_work(unsigned long param)
 static unsigned int _rtl_rx_get_padding(struct ieee80211_hdr *hdr,
 					unsigned int len)
 {
+#if NET_IP_ALIGN != 0
 	unsigned int padding = 0;
+#endif
 
 	/* make function no-op when possible */
 	if (NET_IP_ALIGN == 0 || len < sizeof(*hdr))
 		return 0;
 
+#if NET_IP_ALIGN != 0
 	/* alignment calculation as in lbtf_rx() / carl9170_rx_copy_data() */
 	/* TODO: deduplicate common code, define helper function instead? */
 
@@ -608,6 +609,7 @@ static unsigned int _rtl_rx_get_padding(struct ieee80211_hdr *hdr,
 		padding ^= NET_IP_ALIGN;
 
 	return padding;
+#endif
 }
 
 #define __RADIO_TAP_SIZE_RSV	32