staging/rtl8192u: use s8 instead of char

Compiling the rtlwifi drivers for ARM with gcc -Wextra warns about lots of
incorrect code that results from 'char' being unsigned here, e.g.

staging/rtl8192u/r8192U_core.c:4150:16: error: comparison is always false due to limited range of data type [-Werror=type-limits]
staging/rtl8192u/r8192U_dm.c:646:50: error: comparison is always false due to limited range of data type [-Werror=type-limits]

This patch changes all uses of 'char' in this driver that refer to
8-bit integers to use 's8' instead, which is signed on all architectures.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211.h

@@ -746,7 +746,7 @@ struct ieee80211_rx_stats {
 	bool		  bisrxaggrsubframe;
 	bool		  bPacketBeacon;	//cosa add for rssi
 	bool		  bToSelfBA;		//cosa add for rssi
-	char	  cck_adc_pwdb[4];	//cosa add for rx path selection
+	s8		  cck_adc_pwdb[4];	//cosa add for rx path selection
 	u16		  Seq_Num;
 
 };
@@ -1814,7 +1814,7 @@ struct ieee80211_device {
 	u32 wpax_type_notify; //{added by David, 2006.9.26}
 
 	/* QoS related flag */
-	char init_wmmparam_flag;
+	s8  init_wmmparam_flag;
 	/* set on initialization */
 	u8  qos_support;
 

drivers/staging/rtl8192u/r8192U.h

@@ -533,7 +533,7 @@ typedef struct _rt_9x_tx_rate_history {
 	u32             ht_mcs[4][16];
 } rt_tx_rahis_t, *prt_tx_rahis_t;
 typedef struct _RT_SMOOTH_DATA_4RF {
-	char    elements[4][100]; /* array to store values */
+	s8    elements[4][100]; /* array to store values */
 	u32     index;            /* index to current array to store */
 	u32     TotalNum;         /* num of valid elements */
 	u32     TotalVal[4];      /* sum of valid elements */
@@ -1031,7 +1031,7 @@ typedef struct r8192_priv {
 	s8 cck_present_attentuation;
 	u8 cck_present_attentuation_20Mdefault;
 	u8 cck_present_attentuation_40Mdefault;
-	char cck_present_attentuation_difference;
+	s8 cck_present_attentuation_difference;
 	bool btxpower_tracking;
 	bool bcck_in_ch14;
 	bool btxpowerdata_readfromEEPORM;

drivers/staging/rtl8192u/r8192U_core.c

@@ -4206,7 +4206,7 @@ static void rtl8192_process_phyinfo(struct r8192_priv *priv, u8 *buffer,
  *
  * Return:		0-100 percentage
  *---------------------------------------------------------------------------*/
-static u8 rtl819x_query_rxpwrpercentage(char antpower)
+static u8 rtl819x_query_rxpwrpercentage(s8 antpower)
 {
 	if ((antpower <= -100) || (antpower >= 20))
 		return	0;
@@ -4217,9 +4217,9 @@ static u8 rtl819x_query_rxpwrpercentage(char antpower)
 
 }	/* QueryRxPwrPercentage */
 
-static u8 rtl819x_evm_dbtopercentage(char value)
+static u8 rtl819x_evm_dbtopercentage(s8 value)
 {
-	char ret_val;
+	s8 ret_val;
 
 	ret_val = value;
 
@@ -4294,8 +4294,8 @@ static void rtl8192_query_rxphystatus(struct r8192_priv *priv,
 	phy_ofdm_rx_status_rxsc_sgien_exintfflag *prxsc;
 	u8	*prxpkt;
 	u8	i, max_spatial_stream, tmp_rxsnr, tmp_rxevm, rxsc_sgien_exflg;
-	char	rx_pwr[4], rx_pwr_all = 0;
-	char	rx_snrX, rx_evmX;
+	s8	rx_pwr[4], rx_pwr_all = 0;
+	s8	rx_snrX, rx_evmX;
 	u8	evm, pwdb_all;
 	u32	RSSI, total_rssi = 0;
 	u8	is_cck_rate = 0;
@@ -4420,7 +4420,7 @@ static void rtl8192_query_rxphystatus(struct r8192_priv *priv,
 
 			/* Get Rx snr value in DB */
 			tmp_rxsnr =	pofdm_buf->rxsnr_X[i];
-			rx_snrX = (char)(tmp_rxsnr);
+			rx_snrX = (s8)(tmp_rxsnr);
 			rx_snrX /= 2;
 			priv->stats.rxSNRdB[i] = (long)rx_snrX;
 
@@ -4454,7 +4454,7 @@ static void rtl8192_query_rxphystatus(struct r8192_priv *priv,
 
 		for (i = 0; i < max_spatial_stream; i++) {
 			tmp_rxevm =	pofdm_buf->rxevm_X[i];
-			rx_evmX = (char)(tmp_rxevm);
+			rx_evmX = (s8)(tmp_rxevm);
 
 			/* Do not use shift operation like "rx_evmX >>= 1"
 			 * because the compiler of free build environment will