Partially uninitialized mxt_message on the poller stack when the (device-controlled) T5 object size < 7 — stale stack bytes flow into the user-visible ELO pressure field

Summary

msg is declared uninitialized and filled via mxt_read_object which reads obj->size_minus_one+1 bytes clamped to 7; a device advertising T5 size < 7 leaves msg bytes stale while the read still reports success. msg->touch.amplitude (byte 6) is copied into track->pressure and emitted as ELO packet bytes. Consumer must already be root (0600 node) - defense-in-depth, physical-attacker model. bzero fix.