RDMA/core: Modify rdma_query_gid() to return accurate error codes

Modify rdma_query_gid() to return -ENOENT for empty entries. This will
make error reporting more accurate and will be used in next patches.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Avihai Horon <[e-mail]>
Reviewed-by: Mark Zhang <[e-mail]>
Signed-off-by: Leon Romanovsky <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/core/cache.c

···
 {
 	struct ib_gid_table *table;
 	unsigned long flags;
-	int res = -EINVAL;
+	int res;
 
 	if (!rdma_is_port_valid(device, port_num))
 		return -EINVAL;
···
 	table = rdma_gid_table(device, port_num);
 	read_lock_irqsave(&table->rwlock, flags);
 
-	if (index < 0 || index >= table->sz ||
-	    !is_gid_entry_valid(table->data_vec[index]))
+	if (index < 0 || index >= table->sz) {
+		res = -EINVAL;
 		goto done;
+	}
+
+	if (!is_gid_entry_valid(table->data_vec[index])) {
+		res = -ENOENT;
+		goto done;
+	}
 
 	memcpy(gid, &table->data_vec[index]->attr.gid, sizeof(*gid));
 	res = 0;