Add EDKII_VARIABLE_LOCK_PROTOCOL and the implementation in MdeModulePkg variable drivers.
Add code in BdsDxe driver to call the protocol to mark the read-only variables defined in the UEFI Spec.

Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Guo Dong <guo.dong@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@14372 6f19259b-4bc3-4df7-8a09-765794883524