OvmfPkg: Copy 8254TimerDxe driver from PcAtChipsetPkg

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1496

This commit copies the exact 8254TimerDxe driver from PcAtChipsetPkg to
OvmfPkg.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/8254TimerDxe/8254Timer.inf

@@ -0,0 +1,42 @@
+## @file
+# 8254 timer driver that provides Timer Arch protocol.
+#
+# Copyright (c) 2005 - 2018, Intel Corporation. All rights reserved.<BR>
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = Timer
+  MODULE_UNI_FILE                = Timer.uni
+  FILE_GUID                      = f2765dec-6b41-11d5-8e71-00902707b35e
+  MODULE_TYPE                    = DXE_DRIVER
+  VERSION_STRING                 = 1.0
+
+  ENTRY_POINT                    = TimerDriverInitialize
+
+[Packages]
+  MdePkg/MdePkg.dec
+  IntelFrameworkPkg/IntelFrameworkPkg.dec
+
+[LibraryClasses]
+  UefiBootServicesTableLib
+  BaseLib
+  DebugLib
+  UefiDriverEntryPoint
+  IoLib
+
+[Sources]
+  Timer.h
+  Timer.c
+
+[Protocols]
+  gEfiCpuArchProtocolGuid       ## CONSUMES
+  gEfiLegacy8259ProtocolGuid    ## CONSUMES
+  gEfiTimerArchProtocolGuid     ## PRODUCES
+
+[Depex]
+  gEfiCpuArchProtocolGuid AND gEfiLegacy8259ProtocolGuid
+[UserExtensions.TianoCore."ExtraFiles"]
+  TimerExtra.uni