Change hsail64 DataLayout to use correct pointer sizes.

group, arg, private and spill all must be 32-bit.
Use DataLayout for computing arg pointer size

This probably breaks something
Fix extra pattern to handle lda pointer size conversion
Remove MEMOP32, and try to avoid iPTR

iPTR is fundamentally broken. It pretends to have a pointer type
sometimes, but in general SelectionDAG loses that information.
There's no reasonable way for it to accept an address space, so just
accept any integer type for pointer operands. The custom operand's
base type is still considered to be iPTR, but I'm not sure that really
means anything with suboperands.