SecurityPkg: Tcg2Dxe: Measure DBT into PCR[7]

Measure DBT into PCR[7] in initial measurement phase if present and
not empty by following TCG PC Client PFP 00.49.
The previous patch according to 00.21 is removed
1404e3a1508473643efba89af34bd133ab082dd5

Cc: Star Zeng <star.zeng@intel.com>
Cc: Yao Jiewen <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chao Zhang <chao.b.zhang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Yao Jiewen <jiewen.yao@intel.com>