thunderbolt: Validate XDomain request packet size before type cast

In the Linux kernel, the following vulnerability has been resolved: thunderbolt: Validate XDomain request packet size before type cast tb_xdp_handle_request() casts the received packet buffer to protocol-specific structs without verifying that the allocation is large enough for the target type. A peer can send a minimal XDomain packet that passes the generic header length check but is shorter than the struct accessed after the cast, causing out-of- bounds reads from the kmemdup allocation. Plumb the packet length through xdomain_request_work and validate it against the expected struct size before each cast.