NetworkPkg: Fix the issue cannot boot to UEFI Network after reset

DHCP4 service allows only one of its children to be configured
in the active state,If the DHCP4 D.O.R.A started by IP4 auto
configuration and has not been completed, the Dhcp4 state machine
will not be in the right state for the PXE to start a new round D.O.R.A.
so we need to switch it's policy to static.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18104 6f19259b-4bc3-4df7-8a09-765794883524

NetworkPkg/UefiPxeBcDxe/PxeBcDhcp4.h

@@ -1,7 +1,7 @@
 /** @file
   Functions declaration related with DHCPv4 for UefiPxeBc Driver.
 
-  Copyright (c) 2009 - 2014, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2015, 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
@@ -374,6 +374,20 @@ PxeBcDhcp4Discover (
   IN  EFI_PXE_BASE_CODE_SRVLIST       *SrvList
   );
 
+/**
+  Switch the Ip4 policy to static.
+
+  @param[in]  Private             The pointer to PXEBC_PRIVATE_DATA.
+
+  @retval     EFI_SUCCESS         The policy is already configured to static.
+  @retval     Others              Other error as indicated..
+
+**/
+EFI_STATUS
+PxeBcSetIp4Policy (   
+  IN PXEBC_PRIVATE_DATA            *Private
+  );
+
 
 /**
   Start the D.O.R.A DHCPv4 process to acquire the IPv4 address and other PXE boot information.