eth: ice: drop the dead code related to rss_contexts

ICE appears to have some odd form of rss_context use plumbed
in for .get_rxfh. The .set_rxfh side does not support creating
contexts, however, so this must be dead code. For at least a year
now (since commit 7964e788 ("net: ethtool: use the tracking
array for get_rxfh on custom RSS contexts")) we have not been
calling .get_rxfh with a non-zero rss_context. We just get
the info from the RSS XArray under dev->ethtool.

Remove what must be dead code in the driver, clear the support flags.

Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250707184115.2285277-3-kuba@kernel.org


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