SignedCapsulePkg: Remove redundant things in inf,.h and .c files

SignedCapsulePkg: Remove redundant things in inf,.h and .c files

Two redundant library classes have been removed.
The redundant function "IsSystemFmp" has been removed.
https://bugzilla.tianocore.org/show_bug.cgi?id=1067

v2: Remove DxeServicesLib from SystemFirmwareUpdateDxe.inf.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: shenglei <shenglei.zhang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>