driver core: drop use of BUS_ATTR()

We are trying to get rid of BUS_ATTR() so drop the last user of it from
the tree.  We had to "open code" it in order to prevent a function name
conflict due to the use of DEVICE_ATTR_WO() earlier in the file :(

Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>