iiod: fix shadowed local variable in iiod

Now that we turn this on by default, make sure that this is all OK.

Fixes the warning:
./iiod/ops.c: In function ‘send_data’:
./iiod/ops.c:431:16: warning: declaration of ‘len’ shadows a parameter [-Wshadow]
   ssize_t ret, len;
                ^~~
./iiod/ops.c:415:77: note: shadowed declaration is here
 static ssize_t send_data(struct DevEntry *dev, struct ThdEntry *thd, size_t len)
                                                                      ~~~~~~~^~~

Signed-off-by: Robin Getz <[email protected]>

iiod/ops.c

@@ -428,20 +428,20 @@ static ssize_t send_data(struct DevEntry *dev, struct ThdEntry *thd, size_t len)
 		unsigned int i;
 		char buf[129], *ptr = buf;
 		uint32_t *mask = demux ? thd->mask : dev->mask;
-		ssize_t ret, len;
+		ssize_t ret, length;
 
-		len = sizeof(buf);
+		length = sizeof(buf);
 		/* Send the current mask */
 		for (i = dev->nb_words; i > 0 && ptr < buf + sizeof(buf);
 				i--, ptr += 8) {
-			iio_snprintf(ptr, len, "%08x", mask[i - 1]);
-			len -= 8;
+			iio_snprintf(ptr, length, "%08x", mask[i - 1]);
+			length -= 8;
 		}
 
 		*ptr = '\n';
-		len--;
+		length--;
 
-		if (len < 0) {
+		if (length < 0) {
 			IIO_ERROR("send_data: string length error\n");
 			return -ENOSPC;
 		}