Breaking change issue with NetworkPkg/Ip6Dxe/Ip6ConfigImlp.[c, h]

[Larry Cleeton <Larry.Cleeton@microsoft.com>]

This commit (fdc4b0b147b386e966e99893526181dfae9eaeef) changed a data structure that is stored in an NVRAM variable. 
See NetworkPkg/Ip6Dxe/Ip6ConfigImpl.[c,h]

This data structure:

typedef struct {
  UINT16                    Offset;
  UINTN                     DataSize;
  EFI_IP6_CONFIG_DATA_TYPE  DataType;
} IP6_CONFIG_DATA_RECORD;

Is now:

typedef struct {
  UINT16                    Offset;
  UINT32                     DataSize;    <---------------- changed size in 64bit environments
  EFI_IP6_CONFIG_DATA_TYPE  DataType;
} IP6_CONFIG_DATA_RECORD;

Unfortunately with a 64bit implementation this current structure is now *not* compatible with an existing NVRAM variable written with the previous version of the structure. It's causing me considerable grief so I'm just sharing the discovery.  It would only impact you if you update some 64bit machine's firmware with a new version containing this change.

--Larry