0822201 ShellPkg: Use a local variable to cache the pointer.

Authored and Committed by Jaben Carsey 8 years ago
    ShellPkg: Use a local variable to cache the pointer.
    
    CC: Qiu Shumin <shumin.qiu@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Jaben Carsey <jaben.carsey@intel.com>
    Reviewed-by: Erik Bjorge <erik.c.bjorge@intel.com>
    Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>