sfc: Don't use efx_filter_{build,hash,increment}() for default MAC filters

These functions happen to work for default MAC filters: they generate
an initial index of 1/0 for unicast/multicast respectively and an
increment of 1 for either, so a search succeeds at depth 2.  But this
is a matter of luck rather than design, and it really won't work well
with the bug fix we're about to do.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/filter.c

@@ -463,13 +463,6 @@ static u32 efx_filter_build(efx_oword_t *filter, struct efx_filter_spec *spec)
 		break;
 	}
 
-	case EFX_FILTER_TABLE_RX_DEF:
-		/* One filter spec per type */
-		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);
-		return spec->type - EFX_FILTER_UC_DEF;
-
 	case EFX_FILTER_TABLE_RX_MAC: {
 		bool is_wild = spec->type == EFX_FILTER_MAC_WILD;
 		EFX_POPULATE_OWORD_7(
@@ -667,25 +660,35 @@ s32 efx_filter_insert_filter(struct efx_nic *efx, struct efx_filter_spec *spec,
 	struct efx_filter_spec *saved_spec;
 	efx_oword_t filter;
 	unsigned int filter_idx, depth = 0;
-	u32 key;
 	int rc;
 
 	if (!table || table->size == 0)
 		return -EINVAL;
 
-	key = efx_filter_build(&filter, spec);
-
 	netif_vdbg(efx, hw, efx->net_dev,
 		   "%s: type %d search_depth=%d", __func__, spec->type,
 		   table->search_depth[spec->type]);
 
-	spin_lock_bh(&state->lock);
+	if (table->id == EFX_FILTER_TABLE_RX_DEF) {
+		/* One filter spec per type */
+		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);
+		filter_idx = spec->type - EFX_FILTER_INDEX_UC_DEF;
+
+		spin_lock_bh(&state->lock);
+	} else {
+		u32 key = efx_filter_build(&filter, spec);
+
+		spin_lock_bh(&state->lock);
+
+		rc = efx_filter_search(table, spec, key, &depth);
+		if (rc < 0)
+			goto out;
+		filter_idx = rc;
+		BUG_ON(filter_idx >= table->size);
+	}
 
-	rc = efx_filter_search(table, spec, key, &depth);
-	if (rc < 0)
-		goto out;
-	filter_idx = rc;
-	BUG_ON(filter_idx >= table->size);
 	saved_spec = &table->spec[filter_idx];
 
 	if (test_bit(filter_idx, table->used_bitmap)) {