Add TX support to get/set functions for ethtool coalescing.
tx-frames-irq and tx-usecs-irq can only be set/unset together.
tx-frames-irq needs to be less than TXE and TXB.

As rx and tx share the same timer, rx-usecs-irq and tx-usecs-irq can be
enabled/disabled individually but they need to have the same value if
enabled.

Polling is excluded from TX irq coalescing.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/all/20240207093220.2681425-8-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>