ISAPNP: remove unused pnp_dev->regs field

The "regs" field in struct pnp_dev is set but never read, so remove it.

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>