x86/PV: avoid double stack reset during schedule tail handling

x86/PV: avoid double stack reset during schedule tail handling

Invoking check_wakeup_from_wait() from assembly allows the new
continue_pv_domain() to replace the prior continue_nonidle_domain() as
the tail hook, eliminating an extra reset_stack_and_jump().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>