NetworkPkg/Ip6Dxe: Fix the bug when checking the DataSize
NetworkPkg/Ip6Dxe: Fix the bug when checking the DataSize

During setting the DnsServer, the DataSize check is incorrect.
This patch is to fix the issue.

Cc: Ye Ting <fe1f30c12225d8cd094a72a37b5acbb01ee15159@intel.com>
Cc: Fu Siyuan <eef549df2036636f79f66102b4e2dc444721df8f@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wu Jiaxin <91f509c31e98a6df13950454fe51aea543223eaa@intel.com>
Reviewed-by: Ye Ting <fe1f30c12225d8cd094a72a37b5acbb01ee15159@intel.com>
Reviewed-by: Fu Siyuan <eef549df2036636f79f66102b4e2dc444721df8f@intel.com>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2