commit 
385904f819e3 ('sfc: Don't use
efx_filter_{build,hash,increment}() for default MAC filters') used the
wrong name to find the index of default RX MAC filters at insertion/
update time.  This could result in memory corruption and would in any
case silently fail to update the filter.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
                BUILD_BUG_ON(EFX_FILTER_INDEX_UC_DEF != 0);
                BUILD_BUG_ON(EFX_FILTER_INDEX_MC_DEF !=
                             EFX_FILTER_MC_DEF - EFX_FILTER_UC_DEF);
-               rep_index = spec->type - EFX_FILTER_INDEX_UC_DEF;
+               rep_index = spec->type - EFX_FILTER_UC_DEF;
                ins_index = rep_index;
 
                spin_lock_bh(&state->lock);