ShellPkg: Corrected CatSPrint usage to prevent memory leaks.

ShellPkg: Corrected CatSPrint usage to prevent memory leaks.

CatSPrint allocates return buffer for the caller. The caller doesn't have to allocate one, and has to free the used buffers.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Cecil Sheng <cecil.sheng@hpe.com>
Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18902 6f19259b-4bc3-4df7-8a09-765794883524