hvcs: Use driver groups to manage driver attributes

Rather than manually creating attributes for the hvcs driver,
let the driver core do this for us. This also fixes some hotplug
remove issues and ensures that cleanup of these attributes
is done in the right order.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20230203155802.404324-3-brking@linux.vnet.ibm.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>