MdePkg/BaseLib: Change a variable type in a bitwise operation

MdePkg/BaseLib: Change a variable type in a bitwise operation

Change the type of variable Chr from CHAR8 to UINT32 in a
bitwise operation, to make the two variables in the operation
have the same size.
https://bugzilla.tianocore.org/show_bug.cgi?id=1527

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@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>