RDMA/uverbs: Return not supported error code for unsupported commands

Command that doesn't exist means that it is not supported,
so update code to return -EOPNOTSUPP in case of failure.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/uverbs_main.c

@@ -714,7 +714,7 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 	}
 
 	if (!verify_command_idx(command, extended_command)) {
-		ret = -EINVAL;
+		ret = -EOPNOTSUPP;
 		goto out;
 	}