[SPARC64]: Correctable ECC errors cannot occur at trap level > 0.

The are distrupting, which by the sparc v9 definition means they
can only occur when interrupts are enabled in the %pstate register.
This never occurs in any of the trap handling code running at
trap levels > 0.

So just mark it as an unexpected trap.

This allows us to kill off the cee_stuff member of struct thread_info.

Signed-off-by: David S. Miller <davem@davemloft.net>