Bluetooth: btrtl: validate firmware patch bounds

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: btrtl: validate firmware patch bounds rtlbt_parse_firmware() copies patch_length - 4 bytes before appending the firmware version. A malformed firmware patch shorter than the version field can make this subtraction underflow and turn the copy into an oversized read and write during Bluetooth setup. The existing patch_offset + patch_length check can also wrap on 32-bit architectures. Validate the patch length and range without arithmetic overflow before allocating or copying the patch.