net: igc: let core reject the unsupported coalescing parameters

Set ethtool_ops->supported_coalesce_params to let
the core reject unsupported coalescing parameters.

This driver was rejecting almost all unsupported
parameters already, it was only missing a check
for tx_max_coalesced_frames_irq.

As a side effect of these changes the error code for
unsupported params changes from ENOTSUPP to EOPNOTSUPP.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>