hw/cxl: Check that writes do not go beyond end of target attributes

hw/cxl: Check that writes do not go beyond end of target attributes

In cmd_features_set_feature() the an offset + data size schemed
is used to allow for large features.  Ensure this does not write
beyond the end fo the buffers used to accumulate the full feature
attribute set.

Reported-by: Esifiel <esifiel@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20241101133917.27634-9-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>