Bluetooth: btusb: Fix new sparce warnings

This fix the following warnings detect with make W=1 C=1:

drivers/bluetooth/btusb.c:2212:9: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2212:9: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2245:18: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2249:18: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2253:18: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2257:18: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2261:18: warning: cast to restricted __le16
drivers/bluetooth/btusb.c:2267:18: warning: cast to restricted __le16

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>