sun4u: switch second PCI-ebus bridge BAR over to PCI IO space

The ebus is the sun4u equivalent of the old ISA bus which is already mapped at
the beginning of PCI IO space within QEMU. NetBSD attempts to find the physical
addresses of devices connected to the ebus by parsing the BARs of the PCI-ebus
bridge and using the base address found by matching both the address space
type and range for a particular ebus address.

Since the second PCI-ebus bridge BAR is already aliased onto IO space, switch
the BAR over to match and reduce the size to 0x1000 which is enough to cover
all the legacy ioport devices whilst leaving the remaining IO space for other
PCI devices. This allows NetBSD SPARC64 to correctly detect and access devices
on the ebus.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>