[ScopInfo] Fix: use raw source pointer.
When adding an llvm.memcpy instruction to AliasSetTracker, it uses the raw
source and target pointers which preserve bitcasts.
MemAccInst::getPointerOperand() also returns the raw target pointers, but
Scop::buildAliasGroups() did not for the source pointer. This lead to mismatches
between AliasSetTracker and ScopInfo on which pointer to use.
Fixed by also using raw pointers in Scop::buildAliasGroups().
git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@285071 91177308-0d34-0410-b5e6-96231b3b80d8