ShellPkg: Make the argument type match the function expected parameter type to avoid build fail in GCC45.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Ni Ruiyu <ruiyu.ni@intel.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16163 6f19259b-4bc3-4df7-8a09-765794883524