net/sched: matchall: Avoid overwriting error messages

The various error paths of tc_setup_offload_action() now report specific
error messages. Remove the generic messages to avoid overwriting the
more specific ones.

Before:

 # tc filter add dev dummy0 ingress pref 1 proto all matchall skip_sw action police rate 100Mbit burst 10000
 Error: cls_matchall: Failed to setup flow action.
 We have an error talking to the kernel

After:

 # tc filter add dev dummy0 ingress pref 1 proto all matchall skip_sw action police rate 100Mbit burst 10000
 Error: act_police: Offload not supported when conform/exceed action is "reclassify".
 We have an error talking to the kernel
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_matchall.c

@@ -102,8 +102,6 @@ static int mall_replace_hw_filter(struct tcf_proto *tp,
 	if (err) {
 		kfree(cls_mall.rule);
 		mall_destroy_hw_filter(tp, head, cookie, NULL);
-		NL_SET_ERR_MSG_MOD(cls_mall.common.extack,
-				   "Failed to setup flow action");
 
 		return skip_sw ? err : 0;
 	}
@@ -305,8 +303,6 @@ static int mall_reoffload(struct tcf_proto *tp, bool add, flow_setup_cb_t *cb,
 				      cls_mall.common.extack);
 	if (err) {
 		kfree(cls_mall.rule);
-		NL_SET_ERR_MSG_MOD(cls_mall.common.extack,
-				   "Failed to setup flow action");
 
 		return add && tc_skip_sw(head->flags) ? err : 0;
 	}