MdeModulePkg/Mtftp4Dxe: Separate the timer ticking to calculate the packet live time.

TPL deadlock issue was enrolled by the commit of 39b0867d. To resolve the issue,
this patch separated the timer ticking for all the MTFTP clients to calculate the
packet live time in TPL_NOTIFY level.

Cc: Wang Fan <fan.wang@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Ye Ting <ting.ye@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
(cherry picked from commit 0e2a5749d8)

MdeModulePkg/Universal/Network/Mtftp4Dxe/Mtftp4Support.h

@@ -1,7 +1,7 @@
 /** @file
   Support routines for MTFTP.
   
-Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -187,6 +187,20 @@ Mtftp4Retransmit (
   IN MTFTP4_PROTOCOL        *Instance
   );
 
+/**
+  The timer ticking function in TPL_NOTIFY level for the Mtftp service instance.
+
+  @param  Event                 The ticking event
+  @param  Context               The Mtftp service instance
+
+**/
+VOID
+EFIAPI
+Mtftp4OnTimerTickNotifyLevel (
+  IN EFI_EVENT              Event,
+  IN VOID                   *Context
+  );
+
 /**
   The timer ticking function for the Mtftp service instance.