BaseTools: Library PCD type will inherit from the driver

BaseTools: Library PCD type will inherit from the driver

If a PCD is not referenced in global PCD section of DSC file at all,
but is referenced in module scope, then the default PCD type for libs
should be the module scoped PCD type.

Fixes: https://bugzilla.tianocore.org/show_bug.cgi?id=901
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yunhua Feng <yunhuax.feng@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>