PcAtChipsetPkg/IsaAcpiDxe: Fix VS2012 build failure

PcAtChipsetPkg/IsaAcpiDxe: Fix VS2012 build failure

Done:
if (EFI_ERROR (Status)) {
  if (PciIo != NULL && Enabled) {
    PciIo->Attributes (
             PciIo,
             EfiPciIoAttributeOperationSet,
             OriginalAttributes,
             NULL
             );
  }
}
In above codes, VS2012/VS2010 will report that "OriginalAttributes"
will be used without initialization. But in fact, when the if expression
is true(if (PciIo != NULL && Enabled)), the "OriginalAttributes" must be
initialized. In order to fix this false positive issue, we initialize the
"OriginalAttributes" after declaration.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>