[analyzer] fixed the logic changed by r176949

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@176956 91177308-0d34-0410-b5e6-96231b3b80d8
Fix incorrect cast identification.

Before: int a = sizeof(int *)+ b;"
After:  int a = sizeof(int *) + b;

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@176957 91177308-0d34-0410-b5e6-96231b3b80d8