sfc: unfix not-a-typo in comment

Commit fe09560 ("net: Fix typos") removed duplicated word 'fallback',
 but this was not a typo and change altered the semantic meaning of
 the comment.
Partially revert, using the phrase 'fallback of the fallback' to make
 the meaning more clear to future readers so that they won't try to
 change it again.

Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250731144138.2637949-1-edward.cree@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Edward Cree

drivers/net/ethernet/sfc/tc_encap_actions.c

@@ -442,7 +442,7 @@ static void efx_tc_update_encap(struct efx_nic *efx,
 			rule = container_of(acts, struct efx_tc_flow_rule, acts);
 			if (rule->fallback)
 				fallback = rule->fallback;
-			else /* fallback: deliver to PF */
+			else /* fallback of the fallback: deliver to PF */
 				fallback = &efx->tc->facts.pf;
 			rc = efx_mae_update_rule(efx, fallback->fw_id,
 						 rule->fw_id);