PNP: add pnp_possible_config() -- can a device could be configured this way?

As part of a heuristic to identify modem devices, 8250_pnp.c
checks to see whether a device can be configured at any of the
legacy COM port addresses.

This patch moves the code that traverses the PNP "possible resource
options" from 8250_pnp.c to the PNP subsystem.  This encapsulation
is important because a future patch will change the implementation
of those resource options.

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