intel_iommu: move ce fetching out when sync shadow

intel_iommu: move ce fetching out when sync shadow

There are two callers for vtd_sync_shadow_page_table_range(): one
provided a valid context entry and one not.  Move that fetching
operation into the caller vtd_sync_shadow_page_table() where we need to
fetch the context entry.

Meanwhile, remove the error_report_once() directly since we're already
tracing all the error cases in the previous call.  Instead, return error
number back to caller.  This will not change anything functional since
callers are dropping it after all.

We do this move majorly because we want to do something more later in
vtd_sync_shadow_page_table().

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>