SignedCapsulePkg: Change the SMM debug lib instance

SignedCapsulePkg: Change the SMM debug lib instance

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1416

The UefiDebugLibConOut will not support DXE_SMM_DRIVER,
change UefiDebugLibConOut to BaseDebugLibNull.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Chao Zhang <chao.b.zhang@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Michael Turner <Michael.Turner@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>