net: ethtool: require drivers to set supported_coalesce_params

Now that all in-tree drivers have been updated we can
make the supported_coalesce_params mandatory.

To save debugging time in case some driver was missed
(or is out of tree) add a warning when netdev is registered
with set_coalesce but without supported_coalesce_params.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>