ISAPNP: move config register addresses out of isapnp.h

These are used only in drivers/pnp/isapnp/core.c, so no need to
expose them to the world.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-By: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>