x86_emulate: fold wide reads

x86_emulate: fold wide reads

With HVM's MMIO operand handling now being capable of splitting large
reads, there's no need to issue at most machine word size reads when
we really need wider operands.

Not that this is not done everywhere - there are a couple of cases
where keeping the reads separate is more natural (and folding them
would complicate the code rather than simplifying it).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>