The mode and well-formedness checks above also set fault to True, so we
end up with cases where a DataStore request uses the default load page
fault exception code. Instead, unconditionally set excStorePageFault for
DataStore, and conditionally override to excStoreCapPageFault when
appropriate, being particularly careful to ensure earlier exception
causes still take precedence.
Also restructure the InstFetch and DataLoad cases to match how DataStore
needs to look.
This fixes the rv64si-p-dirty ISA test, currently the sole failure.
e1060ac43d