HID: logitech-hidpp: 2 fixes in hidpp_root_get_protocol_version()

- remove the constant '1'
- when the device is not connected, the protocol error
  HIDPP_ERROR_RESOURCE_ERROR is raised. We should not warn the user about
  it because it is somewhat expected as an answer when we check if the
  device is connected.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-logitech-hidpp.c

@@ -361,12 +361,16 @@ static int hidpp_root_get_protocol_version(struct hidpp_device *hidpp)
 			CMD_ROOT_GET_PROTOCOL_VERSION,
 			NULL, 0, &response);
 
-	if (ret == 1) {
+	if (ret == HIDPP_ERROR_INVALID_SUBID) {
 		hidpp->protocol_major = 1;
 		hidpp->protocol_minor = 0;
 		return 0;
 	}
 
+	/* the device might not be connected */
+	if (ret == HIDPP_ERROR_RESOURCE_ERROR)
+		return -EIO;
+
 	if (ret > 0) {
 		hid_err(hidpp->hid_dev, "%s: received protocol error 0x%02x\n",
 			__func__, ret);