fwctl: pds: Validate RPC input size before parsing

In the Linux kernel, the following vulnerability has been resolved: fwctl: pds: Validate RPC input size before parsing The fwctl core allocates the device-specific RPC input buffer with fwctl_rpc.in_len and passes that buffer to the driver callback. pdsfc_fw_rpc() casts the buffer to struct fwctl_rpc_pds and then calls pdsfc_validate_rpc(), which reads fields from that structure before checking that the input buffer is large enough to contain it. A short in_len can make pds_fwctl read beyond the allocation. Reject pds RPC buffers that are smaller than struct fwctl_rpc_pds before parsing any pds-specific fields.