nds32/setup: remove unused memblock_region variable in setup_memory()

nds32/setup: remove unused memblock_region variable in setup_memory()

kernel test robot reports unused variable warning:

cppcheck possible warnings: (new ones prefixed by >>, may not real
problems)

>> arch/nds32/kernel/setup.c:247:26: warning: Unused variable: region
>> [unusedVariable]
    struct memblock_region *region;
                            ^

Remove the unused variable.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greentime Hu <green.hu@gmail.com>