Bluetooth: btrtl: check for NULL in btrtl_set_quirks()

The btrtl_set_quirks() has accessed btrtl_dev->ic_info->lmp_subver since
b8e482d02513. However, if installing a Realtek Bluetooth controller
without the driver supported, it will hit the NULL point accessed.

Add a check for NULL to avoid the Kernel Oops.

Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>