[clang] Fix noderef for array member of deref expr

    Committing on behalf of thejh (Jann Horn).

    Given an attribute((noderef)) pointer "p" to the struct

    struct s { int a[2]; };
    ensure that the following expressions are treated the same way by the
    noderef logic:

    p->a
    (*p).a
    Until now, the first expression would be treated correctly (nothing is
    added to PossibleDerefs because CheckMemberAccessOfNoDeref() bails out
    on array members), but the second expression would incorrectly warn
    because "*p" creates a PossibleDerefs entry.

    Handle this case the same way as for the AddrOf operator.

    Differential Revision: https://reviews.llvm.org/D92140