[IA64] gensparse_defconfig: turn on PNPACPI

Turn on CONFIG_PNPACPI.  I recently removed 8250_acpi.c.  All devices
previously claimed by 8250_acpi.c should now be claimed by 8250_pnp.c.
This depends on having CONFIG_PNPACPI so ACPI devices show up as PNP
devices.

All other ia64 defconfigs either have CONFIG_PNPACPI already, or
don't have 8250 support turned on at all.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>