sfc: fix deadlock in RSS config read

Since cited commit, core locks the net_device's rss_lock when handling
 ethtool -x command, so driver's implementation should not lock it
 again.  Remove the latter.

Fixes: 040cef3 ("net: ethtool: move get_rxfh callback under the rss_lock")
Reported-by: Damir Mansurov <damir.mansurov@oktetlabs.ru>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1126015
Suggested-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://patch.msgid.link/20260123161634.1215006-1-edward.cree@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Edward Cree

drivers/net/ethernet/sfc/mcdi_filters.c

@@ -2182,12 +2182,7 @@ int efx_mcdi_rx_pull_rss_context_config(struct efx_nic *efx,
 
 int efx_mcdi_rx_pull_rss_config(struct efx_nic *efx)
 {
-	int rc;
-
-	mutex_lock(&efx->net_dev->ethtool->rss_lock);
-	rc = efx_mcdi_rx_pull_rss_context_config(efx, &efx->rss_context);
-	mutex_unlock(&efx->net_dev->ethtool->rss_lock);
-	return rc;
+	return efx_mcdi_rx_pull_rss_context_config(efx, &efx->rss_context);
 }
 
 void efx_mcdi_rx_restore_rss_contexts(struct efx_nic *efx)