OvmfPkg: Set PcdAcpiS3Enable according to QemuFwCfgS3Enabled()

OvmfPkg: Set PcdAcpiS3Enable according to QemuFwCfgS3Enabled()

Also need to declare PcdAcpiS3Enable as DynamicDefault in *.dsc.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>