fix build errors when we enable acpi_piix4 debug

fix build errors when we enable acpi_piix4 debug

I enable acpi_piix4 debug, and got the following build errors:
# make
  CC    libhw64/acpi_piix4.o
cc1: warnings being treated as errors
/home/wency/source/qemu/hw/acpi_piix4.c: In function ‘pm_ioport_write’:
/home/wency/source/qemu/hw/acpi_piix4.c:193: error: format ‘%04x’ expects type ‘unsigned int’, but argument 2 has type ‘uint64_t’
/home/wency/source/qemu/hw/acpi_piix4.c:193: error: format ‘%04x’ expects type ‘unsigned int’, but argument 3 has type ‘uint64_t’
/home/wency/source/qemu/hw/acpi_piix4.c: In function ‘pm_ioport_read’:
/home/wency/source/qemu/hw/acpi_piix4.c:219: error: format ‘%04x’ expects type ‘unsigned int’, but argument 2 has type ‘uint64_t’
make[1]: *** [acpi_piix4.o] Error 1
make: *** [subdir-libhw64] Error 2

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>