MdeModulePkg/BaseResetSystemLibNull.c: Change comments of ResetSystem

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1460

Refer to Uefi spec 2.8, the ResetData is valid while ResetStatus
is EFI_SUCCESS regardless of the ResetType is EfiResetPlatformSpecific
or not.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Michael Turner <Michael.Turner@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Hao Wu <hao.a.wu@intel.com>

MdeModulePkg/Library/BaseResetSystemLibNull/BaseResetSystemLibNull.c

@@ -1,7 +1,7 @@
 /** @file
   Null Reset System Library instance that only generates ASSERT() conditions.
 
-  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -103,9 +103,7 @@ ResetPlatformSpecific (
                             the data buffer starts with a Null-terminated string, optionally
                             followed by additional binary data. The string is a description
                             that the caller may use to further indicate the reason for the
-                            system reset. ResetData is only valid if ResetStatus is something
-                            other than EFI_SUCCESS unless the ResetType is EfiResetPlatformSpecific
-                            where a minimum amount of ResetData is always required.
+                            system reset.
 **/
 VOID
 EFIAPI