MIPS: Malta: Setup PM I/O region on boot

This patch ensures that the kernel sets a sane base address for the
PIIX4 PM I/O register region during boot. Without this the kernel may
not successfully claim the region as a resource if the bootloader didn't
configure the region. With this patch the kernel will always succeed
with:

  pci 0000:00:0a.3: quirk: [io  0x1000-0x103f] claimed by PIIX4 ACPI

The lack of the resource claiming is easily reproducible without this
patch using current versions of QEMU.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Tested-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6641/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>