ArmVirtPkg, OvmfPkg: retire QemuFwCfgS3Enabled() from QemuFwCfgLib

At this point we're ready to retire QemuFwCfgS3Enabled() from the
QemuFwCfgLib class, together with its implementations in:

- ArmVirtPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
- OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c

Extend all modules that call the function with a new QemuFwCfgS3Lib class
dependency. Thanks to the previously added library class, instances, and
class resolutions, we can do this switch now as tightly as possible.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=394
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c

@@ -368,31 +368,3 @@ QemuFwCfgFindFile (
 
   return RETURN_NOT_FOUND;
 }
-
-
-/**
-  Determine if S3 support is explicitly enabled.
-
-  @retval  TRUE   if S3 support is explicitly enabled.
-           FALSE  otherwise. This includes unavailability of the firmware
-                  configuration interface.
-**/
-BOOLEAN
-EFIAPI
-QemuFwCfgS3Enabled (
-  VOID
-  )
-{
-  RETURN_STATUS        Status;
-  FIRMWARE_CONFIG_ITEM FwCfgItem;
-  UINTN                FwCfgSize;
-  UINT8                SystemStates[6];
-
-  Status = QemuFwCfgFindFile ("etc/system-states", &FwCfgItem, &FwCfgSize);
-  if (Status != RETURN_SUCCESS || FwCfgSize != sizeof SystemStates) {
-    return FALSE;
-  }
-  QemuFwCfgSelectItem (FwCfgItem);
-  QemuFwCfgReadBytes (sizeof SystemStates, SystemStates);
-  return (BOOLEAN) (SystemStates[3] & BIT7);
-}