ipc: Remove device io_active flag

Nothing used this feature, so removing it.

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2636>

src/xrt/ipc/server/ipc_server.h

···
 {
 	//! The actual device.
 	struct xrt_device *xdev;
-
-	//! Is the IO suppressed for this device.
-	bool io_active;
 };
 
 /*!

src/xrt/ipc/server/ipc_server_handler.c

···
 // Copyright 2020-2024, Collabora, Ltd.
+// Copyright 2025, NVIDIA CORPORATION.
 // SPDX-License-Identifier: BSL-1.0
 /*!
  * @file
···
 }
 
 xrt_result_t
-ipc_handle_system_toggle_io_device(volatile struct ipc_client_state *ics, uint32_t device_id)
-{
-	if (device_id >= IPC_MAX_DEVICES) {
-		return XRT_ERROR_IPC_FAILURE;
-	}
-
-	struct ipc_device *idev = &ics->server->idevs[device_id];
-
-	idev->io_active = !idev->io_active;
-
-	return XRT_SUCCESS;
-}
-
-xrt_result_t
 ipc_handle_swapchain_get_properties(volatile struct ipc_client_state *ics,
                                     const struct xrt_swapchain_create_info *info,
                                     struct xrt_swapchain_create_properties *xsccp)
···
 	struct xrt_input *dst = &ism->inputs[isdev->first_input_index];
 	size_t size = sizeof(struct xrt_input) * isdev->input_count;
 
-	bool io_active = ics->io_active && idev->io_active;
+	bool io_active = ics->io_active;
 	if (io_active) {
 		memcpy(dst, src, size);
 	} else {
···
 	}
 
 	// Special case the headpose.
-	bool disabled = (!isdev->io_active || !ics->io_active) && name != XRT_INPUT_GENERIC_HEAD_POSE;
+	bool disabled = !ics->io_active && name != XRT_INPUT_GENERIC_HEAD_POSE;
 	bool active_on_client = input->active;
 
 	// We have been disabled but the client hasn't called update.

src/xrt/ipc/server/ipc_server_process.c

···
 static void
 init_idev(struct ipc_device *idev, struct xrt_device *xdev)
 {
-	if (xdev != NULL) {
-		idev->io_active = true;
-		idev->xdev = xdev;
-	} else {
-		idev->io_active = false;
-	}
+	idev->xdev = xdev;
 }
 
 static void
 teardown_idev(struct ipc_device *idev)
 {
-	idev->io_active = false;
+	idev->xdev = NULL;
 }
 
 static void

src/xrt/ipc/shared/proto.json

···
 		]
 	},
 
-	"system_toggle_io_device": {
-		"in": [
-			{"name": "id", "type": "uint32_t"}
-		]
-	},
-
 	"system_devices_get_roles": {
 		"out": [
 			{"name": "system_roles", "type": "struct xrt_system_roles"}