sfc: Check firmware supports Ethernet PTP filter

Not all firmware variants support RSS filters. Do not fail all PTP
functionality when raw ethernet PTP filters fail to insert.

Fixes: e4616f64 ("sfc: support PTP over Ethernet")
Signed-off-by: Alex Austin <alex.austin@amd.com>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Link: https://lore.kernel.org/r/20230824164657.42379-1-alex.austin@amd.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>