OvmfPkg/QemuFlashFvbServices: factor out SetPcdFlashNvStorageBaseAddresses

Extract the dynamic setting of the
- PcdFlashNvStorageVariableBase64
- PcdFlashNvStorageFtwWorkingBase
- PcdFlashNvStorageFtwSpareBase
addresses to a helper function.

For now, the helper function is identical (duplicated) between the SMM
flash driver and the runtime DXE flash driver. In subsequent patches, this
will change.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=386
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200310222739.26717-3-lersek@redhat.com>
Acked-by: Leif Lindholm <leif@nuviainc.com>

OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FwBlockService.c

@@ -1051,24 +1051,7 @@ FvbInitialize (
 
   MarkIoMemoryRangeForRuntimeAccess (BaseAddress, Length);
 
-  //
-  // Set several PCD values to point to flash
-  //
-  PcdStatus = PcdSet64S (
-    PcdFlashNvStorageVariableBase64,
-    (UINTN) PcdGet32 (PcdOvmfFlashNvStorageVariableBase)
-    );
-  ASSERT_RETURN_ERROR (PcdStatus);
-  PcdStatus = PcdSet32S (
-    PcdFlashNvStorageFtwWorkingBase,
-    PcdGet32 (PcdOvmfFlashNvStorageFtwWorkingBase)
-    );
-  ASSERT_RETURN_ERROR (PcdStatus);
-  PcdStatus = PcdSet32S (
-    PcdFlashNvStorageFtwSpareBase,
-    PcdGet32 (PcdOvmfFlashNvStorageFtwSpareBase)
-    );
-  ASSERT_RETURN_ERROR (PcdStatus);
+  SetPcdFlashNvStorageBaseAddresses ();
 
   FwhInstance = (EFI_FW_VOL_INSTANCE *)
     (