PNP: factor pnp_init_resource_table() and pnp_clean_resource_table()

Move the common part of pnp_init_resource_table() and
pnp_clean_resource_table() into a new pnp_init_resource().
This reduces a little code duplication and will be
useful later to initialize an individual resource.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>