bluetooth: host: att: Remove meaningless check

`>= 0` was used when EATT support was implemented (zephyrproject-rtos#23199) because
`bt_l2cap_chan_send` could return number of bytes sent. After PR zephyrproject-rtos#67528,
`bt_l2cap_chan_send` doesn't return amount of bytes sent or any positive
value, but either 0 or negative value. Thus `>= 0` is not needed. It
also confusing when reading code, especially when the same check is not
implemented in other cases where underlying function `chan_send` is
used.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>

Author: PavelVPV

subsys/bluetooth/host/att.c

@@ -584,7 +584,8 @@ static void bt_att_sent(struct bt_l2cap_chan *ch)
 	if (!chan->req && !sys_slist_is_empty(&att->reqs)) {
 		sys_snode_t *node = sys_slist_get(&att->reqs);
 
-		if (bt_att_chan_req_send(chan, ATT_REQ(node)) >= 0) {
+		err = bt_att_chan_req_send(chan, ATT_REQ(node));
+		if (!err) {
 			return;
 		}
 
@@ -919,7 +920,7 @@ static void att_req_send_process(struct bt_att *att)
 			continue;
 		}
 
-		if (bt_att_chan_req_send(chan, req) >= 0) {
+		if (!bt_att_chan_req_send(chan, req)) {
 			return;
 		}
 
@@ -3346,7 +3347,7 @@ static void bt_att_status(struct bt_l2cap_chan *ch, atomic_t *status)
 		return;
 	}
 
-	if (bt_att_chan_req_send(chan, ATT_REQ(node)) >= 0) {
+	if (!bt_att_chan_req_send(chan, ATT_REQ(node))) {
 		return;
 	}