enic: remove copybreak tunable

enic: remove copybreak tunable

With the move to using the Page Pool API for RX, rx copybreak was not
showing any improvement in host CPU overhead, latency or bandwidth so
the driver no longer makes use of the rx_copybreak setting. This patch
removes the ethtool tuneable hooks to set and get the rx copybreak since
they and now no-ops. Rx copybreak was the only tunable supported, so
remove the set and get tunable callbacks all together.

Co-developed-by: Nelson Escobar <neescoba@cisco.com>
Signed-off-by: Nelson Escobar <neescoba@cisco.com>
Co-developed-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: John Daley <johndale@cisco.com>
Link: https://patch.msgid.link/20250205235416.25410-5-johndale@cisco.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>