ehea: Fixing LRO configuration

In order to set LRO on ehea, the user must set a module parameter, which
is not the standard way to do so. This patch adds a way to set LRO using
the ethtool tool.

Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>