[ScopInfo] Fix check for element size mismatch.

The way to get the elements size with getPrimitiveSizeInBits() is not
the same as used in other parts of Polly which should use
DataLayout::getTypeAllocSize(). Its use only queries the size of the
pointer and getPrimitiveSizeInBits returns 0 for types that require a
DataLayout object such as pointers.

Together with r265379, this should fix PR27195.

llvm-svn: 265795