https://bugzilla.tianocore.org/show_bug.cgi?id=2088
If there are more than one override instance for a same module,
the Module Unique Name is generated incorrectly.
Cc: Liming Gao <liming.gao@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>