MdeModulePkg: Drop VarLock from RuntimeDxe variable driver

MdeModulePkg: Drop VarLock from RuntimeDxe variable driver

https://bugzilla.tianocore.org/show_bug.cgi?id=2522

Now that everything should be moved to
VariablePolicy, drop support for the
deprecated VarLock SMI interface and
associated functions from variable RuntimeDxe.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Bret Barkelew <brbarkel@microsoft.com>
Signed-off-by: Bret Barkelew <brbarkel@microsoft.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Acked-by: Jian J Wang <jian.j.wang@intel.com>