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

CC: Qiu Shumin <a85ffd5e6451a83645d9ceae55f1cb6cdf90c130@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jaben Carsey <2d4ee76b36e91bee3a58378b7538904eb027a616@intel.com>
Reviewed-by: Erik Bjorge <330ad10f99fcdfb914fa4e3b5d9f2ec8c03e31ae@intel.com>
Reviewed-by: Qiu Shumin <a85ffd5e6451a83645d9ceae55f1cb6cdf90c130@intel.com>

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