wireless: at76c50x: use native hex_pack_byte() method

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "John W. Linville" <linville@tuxdriver.com>
Tested-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/at76c50x-usb.c

@@ -500,10 +500,9 @@ exit:
 
 #define HEX2STR_BUFFERS 4
 #define HEX2STR_MAX_LEN 64
-#define BIN2HEX(x) ((x) < 10 ? '0' + (x) : (x) + 'A' - 10)
 
 /* Convert binary data into hex string */
-static char *hex2str(void *buf, int len)
+static char *hex2str(void *buf, size_t len)
 {
 	static atomic_t a = ATOMIC_INIT(0);
 	static char bufs[HEX2STR_BUFFERS][3 * HEX2STR_MAX_LEN + 1];
@@ -514,18 +513,17 @@ static char *hex2str(void *buf, int len)
 	if (len > HEX2STR_MAX_LEN)
 		len = HEX2STR_MAX_LEN;
 
-	if (len <= 0) {
-		ret[0] = '\0';
-		return ret;
-	}
+	if (len == 0)
+		goto exit;
 
 	while (len--) {
-		*obuf++ = BIN2HEX(*ibuf >> 4);
-		*obuf++ = BIN2HEX(*ibuf & 0xf);
+		obuf = pack_hex_byte(obuf, *ibuf++);
 		*obuf++ = '-';
-		ibuf++;
 	}
-	*(--obuf) = '\0';
+	obuf--;
+
+exit:
+	*obuf = '\0';
 
 	return ret;
 }