HID: logitech-hidpp: Silence intermittent get_battery_capacity errors

My Logitech M185 (PID:4038) 2.4 GHz wireless HID++ mouse is causing
intermittent errors like these in the log:

[11091.034857] logitech-hidpp-device 0003:046D:4038.0006: hidpp20_batterylevel_get_battery_capacity: received protocol error 0x09
[12388.031260] logitech-hidpp-device 0003:046D:4038.0006: hidpp20_batterylevel_get_battery_capacity: received protocol error 0x09
[16613.718543] logitech-hidpp-device 0003:046D:4038.0006: hidpp20_batterylevel_get_battery_capacity: received protocol error 0x09
[23529.938728] logitech-hidpp-device 0003:046D:4038.0006: hidpp20_batterylevel_get_battery_capacity: received protocol error 0x09

We are already silencing error-code 0x09 (HIDPP_ERROR_RESOURCE_ERROR)
errors in other places, lets do the same in
hidpp20_batterylevel_get_battery_capacity to remove these harmless,
but scary looking errors from the dmesg output.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-logitech-hidpp.c

@@ -1102,6 +1102,9 @@ static int hidpp20_batterylevel_get_battery_capacity(struct hidpp_device *hidpp,
 	ret = hidpp_send_fap_command_sync(hidpp, feature_index,
 					  CMD_BATTERY_LEVEL_STATUS_GET_BATTERY_LEVEL_STATUS,
 					  NULL, 0, &response);
+	/* Ignore these intermittent errors */
+	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);