BaseTools/PeCoffLoaderEx: Remove the unused local variable

BZ:2864 GCC build fails due to variable self assignment.

This local variable is not used at any where, we can just remove it.

Signed-off-by: Abner Chang <abner.chang@hpe.com>

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>