pci: fix bridge IO/BASE

commit 5caef97a16010f818ea8b950e2ee24ba876643ad introduced
a regression: we do not make IO base/limit upper 16
bit registers writeable, so we should report a 16 bit
IO range type, not a 32 bit one.
Note that PCI_PREF_RANGE_TYPE_32 is 0x0, but PCI_IO_RANGE_TYPE_32 is 0x1.

In particular, this broke sparc64.

Note: this just reverts to behaviour prior to the commit above.
Making PCI_IO_BASE_UPPER16 and PCI_IO_LIMIT_UPPER16
registers writeable should, and seems to, work just as well, but
as no system seems to actually be interested in 32 bit IO,
let's not make unnecessary changes.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
