ravb: Remove Rx overflow log messages

Remove Rx overflow log messages as in an environment where logging results
in network traffic logging may cause further overflows.

Fixes: c156633f ("Renesas Ethernet AVB driver proper")
Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
[simon: reworked changelog]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>