staging: octeon-ethernet: remove skb alloc failure warnings

Remove skb allocation failure warnings. They will trigger a page
allocation warning already. Also, one of the warnings was not ratelimited,
causing the box to lock up under heavy traffic & low memory.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: David Daney <david.daney@cavium.com>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>