sh_eth: fix comment grammar in 'struct sh_eth_cpu_data'

All the verbs in the comments to the 'struct sh_eth_cpu_data' declaration
should  be in a  3rd person singular, to match the nouns.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>