Fix GCC build fail issue for MdeModulePkg and NetworkPkg.

Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
Reviewed-by: Ouyang Qian <qian.ouyang@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14007 6f19259b-4bc3-4df7-8a09-765794883524

NetworkPkg/Ip6Dxe/Ip6Common.c

@@ -339,10 +339,11 @@ Ip6AddAddr (
 
 **/
 EFI_STATUS
+EFIAPI
 Ip6DestroyChildEntryByAddr (
   IN LIST_ENTRY         *Entry,
   IN VOID               *Context
-)
+  )
 {
   IP6_PROTOCOL                  *Instance;
   EFI_SERVICE_BINDING_PROTOCOL  *ServiceBinding;

NetworkPkg/Ip6Dxe/Ip6Driver.c

@@ -584,10 +584,11 @@ Ip6DriverBindingStart (
 
 **/
 EFI_STATUS
+EFIAPI
 Ip6DestroyChildEntryInHandleBuffer (
   IN LIST_ENTRY         *Entry,
   IN VOID               *Context
-)
+  )
 {
   IP6_PROTOCOL                  *IpInstance;
   EFI_SERVICE_BINDING_PROTOCOL  *ServiceBinding;