Add the possibility to set coalescing parameters with ethtool.

rx-frames-irq and rx-usecs-irq can only be set and unset together as the
implemented mechanism would not work otherwise. rx-frames-irq can't be
greater than the RX FIFO size.

Also all values can only be changed if the chip is not active.

Polling is excluded from irq coalescing support.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/all/20240207093220.2681425-7-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>