BaseTools/DevicePath: Add a checking step

BaseTools/DevicePath: Add a checking step

Add a checking step in DevicePathUtilities.c
to verify DevicePath.
https://bugzilla.tianocore.org/show_bug.cgi?id=1372

v2: Remove ASSERT() and the redundant checking step.
    Update related description.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>