RDMA/nes: Use ethtool timer value

Use timer value set via ethtool intead of #defines.

Signed-off-by: John Lacombe <jlacombe@neteffect.com>
Signed-off-by: Sweta Bhatt <sweta.bhatt@einfochips.com>
Signed-off-by: Chien Tung <ctung@neteffect.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>