Bluetooth: btnxpuart: Validate the FW dump header length

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: btnxpuart: Validate the FW dump header length nxp_process_fw_dump() pulls the ACL header off the frame and then reads seq_num and buf_len from a struct nxp_fw_dump_hdr placed at skb->data, without checking that the ACL payload is long enough to contain it. h4_recv_buf() collects HCI_ACL_HDR_SIZE bytes of header followed by the number of payload bytes named in that header, so skb->len is 4 + dlen with dlen supplied by the controller and possibly smaller than the 8 byte dump header, or zero. A short frame with connection handle 0xfff therefore reads both fields from beyond the received data. Beyond the read itself, buf_len is what terminates a dump: a value of zero makes the driver call hci_devcd_complete() and reset the controller, so a truncated frame can end a dump early. Use skb_pull_data() to validate and pull the FW dump header before accessing its fields. Warn and reject the chunk if the header is truncated.