ethtool: add two coalesce attributes for CQE mode

Currently, there are many drivers who support CQE mode configuration,
some configure it as a fixed when initialized, some provide an
interface to change it by ethtool private flags. In order to make it
more generic, add two new 'ETHTOOL_A_COALESCE_USE_CQE_TX' and
'ETHTOOL_A_COALESCE_USE_CQE_RX' coalesce attributes, then these
parameters can be accessed by ethtool netlink coalesce uAPI.

Also add an new structure kernel_ethtool_coalesce, then the
new parameter can be added into this struct.

Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>