node_device: fix libvirt build if WITH_HAL is defined
    
    commit ffc40b63b50ecb changed uniond _virNodeDevCapData into a typedef
    named virNodeDevCapData with a struct that contains the union as well
    as a type enum. This change necessitated changing every reference to
    "caps->type" into "caps->data.type", but the author of that patch
    failed to test a build "WITH_HAL". This patch fixes the one place in
    the hal backend that needed changing.