trace: allow for different sub-classes of TRC_PV_* tracepoints

trace: allow for different sub-classes of TRC_PV_* tracepoints

We want to add additional sub-classes for TRC_PV tracepoints and to be
able to only capture these new sub-classes.  This cannot currently be
done as the existing tracepoints all use a sub-class of 0xf.

So, redefine the PV events to use a new sub-class.  All the current
tracepoints are tracing entry points to the hypervisor so the
sub-class is named TRC_PV_ENTRY.

This change does not affect xenalyze as that only looks at the main
class and the event number and does not use the sub-class field.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Committed-by: Keir Fraser <keir@xen.org>