Move property cloning code into its own routine

Split the pieces of dlpar_clone_drconf_property() that create a copy of
the property struct into its own routine. This allows for creating
clones of more than just the ibm,dynamic-memory property used in memory
hotplug.
Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>