[LSR] Support SCEVPtrToAddr in SCEVDbgValueBuilder.
Allow SCEVPtrToAddr as cast in assertion in SCEVDbgValueBuilder.
SCEVPtrToAddr is handled similarly to SCEVPtrToInt.
Fixes a crash with debug info after bd40d1de9c9ee, which started to
generate ptrtoaddr instead of ptrtoint expressions.
