HID: huion: Fix sparse warnings

Fix sparse warnings in hid-huion.c by using correct buffer type for
retrieved string descriptor.

The warnings in question were:

    drivers/hid/hid-huion.c:144:44: sparse: cast to restricted __le16
    drivers/hid/hid-huion.c:145:44: sparse: cast to restricted __le16
    drivers/hid/hid-huion.c:146:51: sparse: cast to restricted __le16
    drivers/hid/hid-huion.c:147:30: sparse: cast to restricted __le16

Reported-by: fengguang.wu@intel.com
Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-huion.c

@@ -115,7 +115,7 @@ static int huion_tablet_enable(struct hid_device *hdev)
 	int rc;
 	struct usb_device *usb_dev = hid_to_usb_dev(hdev);
 	struct huion_drvdata *drvdata = hid_get_drvdata(hdev);
-	u16 buf[6];
+	__le16 buf[6];
 
 	/*
 	 * Read string descriptor containing tablet parameters. The specific