viridian: log initial invocation of each type of hypercall

viridian: log initial invocation of each type of hypercall

To make is simpler to observe which viridian hypercalls are issued by a
particular Windows guest, this patch adds a per-domain mask to track them.
Each type of hypercall causes a different bit to be set in the mask and
when the bit transitions from clear to set, a log line is emitted showing
the name of the hypercall and the domain that issued it.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Acked-by: Wei Liu <wl@xen.org>