qemu:Disable balloon_fix_value case in ppc64

ppc64 platform does not support X86 ACPI s3 and s4 cases,
disable it in ppc64 platform

Signed-off-by: Man Li <limansh@cn.ibm.com>
Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Merge pull request #1307 from QiuMike/Disable_balloon_fix_value_case

Disable balloon_fix_value case in ppc64 platform