[SelectionDAG] Correct AddNodeIDCustom for MemIntrinsicSDNodes.

We were missing any support for ISD::INTRINSIC_W_CHAIN/INTRINSIC_VOID
used for memory operations.

For ISD::PREFETCH and target memory nodes we didn't add the subclass
data.

This patch handles all MemIntrinsicSDNode in one place and adds the
missing subclass data.

Note. Unlike load/stores we don't add the memory VT in AddNodeIDCustom or getMemIntrinsicNode. Not sure why.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D150387