vfio/amba: Mark for removal

vfio-amba has only been touched to keep up with the rest of the code
base for the past 10 years.  We have no basis to believe that it's
currently tested or used.  Mark it for deprecation.

Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20250825175807.3264083-2-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Author: Alex Williamson

drivers/vfio/platform/Kconfig

@@ -17,10 +17,13 @@ config VFIO_PLATFORM
 	  If you don't know what to do here, say N.
 
 config VFIO_AMBA
-	tristate "VFIO support for AMBA devices"
+	tristate "VFIO support for AMBA devices (DEPRECATED)"
 	depends on ARM_AMBA || COMPILE_TEST
 	select VFIO_PLATFORM_BASE
 	help
+	  The vfio-amba driver is deprecated and will be removed in a
+	  future kernel release.
+
 	  Support for ARM AMBA devices with VFIO. This is required to make
 	  use of ARM AMBA devices present on the system using the VFIO
 	  framework.

drivers/vfio/platform/vfio_amba.c

@@ -70,6 +70,8 @@ static int vfio_amba_probe(struct amba_device *adev, const struct amba_id *id)
 	struct vfio_platform_device *vdev;
 	int ret;
 
+	dev_err_once(&adev->dev, "DEPRECATION: vfio-amba is deprecated and will be removed in a future kernel release\n");
+
 	vdev = vfio_alloc_device(vfio_platform_device, vdev, &adev->dev,
 				 &vfio_amba_ops);
 	if (IS_ERR(vdev))