More demo work, cleanup

src/m_Do/m_Do_MemCardRWmng.cpp

@@ -306,8 +306,7 @@ u32 mDoMemCdRWm_CalcCheckSum(void* p_, u32 size) {
 u16 mDoMemCdRWm_CalcCheckSumPictData(void* p, u32 size) {
     u16 csum = 0;
     for (int i = 0; i < size; i++) {
-        u8 v = ((u8*)p)[i];
-        csum += v;
+        csum += ((u8*)p)[i];
     }
     return csum;
 }