qcacld-3.0: Return the number of bytes placed in to the buffer

When the sysfs file 'gtx_bw_mask' is read, DEVICE_ATTR 'show' callback
function is called and currently its returning 'ret' which is 0 and hence
the content of sysfs file "/sys/class/net/wlanxx/gtx_bw_mask" is empty.

Hence the fix is 'show' callback function should return the number of
bytes placed in to the buffer.

Change-Id: I44b7eda40cd2963b4be52f97b513badc48244120
CRs-Fixed: 2720141

core/hdd/src/wlan_hdd_sysfs_gtx_bw_mask.c

@@ -163,9 +163,7 @@ __hdd_sysfs_gtx_bw_mask_show(struct net_device *net_dev, char *buf)
 		return -EINVAL;
 	}
 
-	scnprintf(buf, PAGE_SIZE, "%d", value);
-
-	return ret;
+	return scnprintf(buf, PAGE_SIZE, "%d", value);
 }
 
 static ssize_t