exec: simplify address_space_get_iotlb_entry

exec: simplify address_space_get_iotlb_entry

This patch let address_space_get_iotlb_entry() to use the newly
introduced page_mask parameter in flatview_do_translate(). Then we
will be sure the IOTLB can be aligned to page mask, also we should
nicely support huge pages now when introducing a764040.

Fixes: a764040 ("exec: abstract address_space_do_translate()")
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20171010094247.10173-3-maxime.coquelin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>